diff --git a/.eslintignore b/.eslintignore
index 3d61567..6e35e5d 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -2,4 +2,5 @@ node_modules/
 .DS_Store
 lib/
 .husky
-dist/
\ No newline at end of file
+dist/
+vendor/
\ No newline at end of file
diff --git a/data/google-analytics.json b/data/google-analytics.json
index 2d2ad24..ed03bba 100644
--- a/data/google-analytics.json
+++ b/data/google-analytics.json
@@ -15,18 +15,12 @@
       "key": "gtag"
     },
     {
-      "code": "window[{{l}}]=window[{{l}}]||[];window['gtag-'+{{l}}]=function (){window[{{l}}].push(arguments);};window['gtag-'+{{l}}]('consent', {{consentType}}, {{consentValues}});window['gtag-'+{{l}}]('js',new Date());window['gtag-'+{{l}}]('config',{{id}})",
+      "code": "window[{{l}}]=window[{{l}}]||[];window['gtag-'+{{l}}]=function (){window[{{l}}].push(arguments);};{{#consentValues}}window['gtag-'+{{l}}]('consent', {{consentType}}, {{consentValues}});{{/consentValues}}window['gtag-'+{{l}}]('js',new Date());window['gtag-'+{{l}}]('config',{{id}})",
       "params": ["id"],
       "optionalParams": {
         "l": "dataLayer",
         "consentType": "default",
-        "consentValues": {
-          "ad_user_data": "denied",
-          "ad_personalization": "denied",
-          "ad_storage": "denied",
-          "analytics_storage": "denied",
-          "wait_for_update": 500
-        }
+        "consentValues": null
       },
       "strategy": "worker",
       "location": "head",
diff --git a/inc/Data/ThirdPartyDataFormatter.php b/inc/Data/ThirdPartyDataFormatter.php
index 5dfd179..e83d1a8 100644
--- a/inc/Data/ThirdPartyDataFormatter.php
+++ b/inc/Data/ThirdPartyDataFormatter.php
@@ -20,7 +20,7 @@ class ThirdPartyDataFormatter
     /**
      * Formats third party data for a given set of input arguments and returns the corresponding output.
      *
-     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/0831b937a8468e0f74bd79edd5a59fa8b2e6e763/src/utils/index.ts#L94
+     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/54cd44d1bd197a7809ab2f6ede4d13a973087c3d/src/utils/index.ts#L105
      *
      * @param ThirdPartyData       $data Third party data to format.
      * @param array<string, mixed> $args Input arguments to format third party data with.
@@ -31,15 +31,20 @@ public static function formatData(ThirdPartyData $data, array $args): ThirdParty
         $htmlData    = $data->getHtml();
         $scriptsData = $data->getScripts();
 
-        $allScriptParams = array_reduce(
-            $scriptsData,
-            static function ($acc, ThirdPartyScriptData $scriptData) {
-                foreach ($scriptData->getParams() as $param) {
-                    $acc[] = $param;
-                }
-                return $acc;
-            },
-            []
+        $allScriptParams = array_unique(
+            array_reduce(
+                $scriptsData,
+                static function ($acc, ThirdPartyScriptData $scriptData) {
+                    foreach ($scriptData->getParams() as $param) {
+                        $acc[] = $param;
+                    }
+                    foreach (array_keys($scriptData->getOptionalParams()) as $param) {
+                        $acc[] = $param;
+                    }
+                    return $acc;
+                },
+                []
+            )
         );
 
         $scriptUrlParamInputs = self::intersectArgs($args, $allScriptParams);
@@ -84,20 +89,24 @@ static function ($acc, ThirdPartyScriptData $scriptData) {
         }
         if (isset($newData['scripts']) && $newData['scripts']) {
             $newData['scripts'] = array_map(
-                static function ($scriptData) use ($scriptUrlParamInputs) {
+                static function ($scriptData) use ($args) {
                     if (isset($scriptData['url'])) {
                         $scriptData['url'] = self::formatUrl(
                             $scriptData['url'],
-                            $scriptData['params'],
-                            $scriptUrlParamInputs
+                            $scriptData['params'] ?? [],
+                            $args,
+                            [],
+                            $scriptData['optionalParams'] ?? []
                         );
                     } else {
                         $scriptData['code'] = self::formatCode(
                             $scriptData['code'],
-                            $scriptUrlParamInputs
+                            $args,
+                            $scriptData['optionalParams'] ?? []
                         );
                     }
-                    unset($scriptData['params']); // Params are irrelevant for formatted output.
+                    // Params are irrelevant for formatted output.
+                    unset($scriptData['params'], $scriptData['optionalParams']);
                     return $scriptData;
                 },
                 $newData['scripts']
@@ -110,7 +119,7 @@ static function ($scriptData) use ($scriptUrlParamInputs) {
     /**
      * Formats the given HTML arguments into an HTML string.
      *
-     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/0831b937a8468e0f74bd79edd5a59fa8b2e6e763/src/utils/index.ts#L55
+     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/54cd44d1bd197a7809ab2f6ede4d13a973087c3d/src/utils/index.ts#L66
      *
      * @param string               $element           Element tag name for the HTML element.
      * @param array<string, mixed> $attributes        Attributes for the HTML element.
@@ -152,17 +161,24 @@ public static function formatHtml(
     /**
      * Formats the given URL arguments into a URL string.
      *
-     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/0831b937a8468e0f74bd79edd5a59fa8b2e6e763/src/utils/index.ts#L28
+     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/54cd44d1bd197a7809ab2f6ede4d13a973087c3d/src/utils/index.ts#L28
      *
-     * @param string               $url          Base URL.
-     * @param string[]             $params       Parameter names.
-     * @param array<string, mixed> $args         Input arguments for the src attribute query parameters.
-     * @param array<string, mixed> $slugParamArg Optional. Input argument for the src attribute slug query parameter.
-     *                                           Default empty array.
+     * @param string               $url            Base URL.
+     * @param string[]             $params         Parameter names.
+     * @param array<string, mixed> $args           Input arguments for the src attribute query parameters.
+     * @param array<string, mixed> $slugParamArg   Optional. Input argument for the src attribute slug query parameter.
+     *                                             Default empty array.
+     * @param array<string, mixed> $optionalParams Optional. Optional parameter names and their defaults.
+     *                                             Default empty array.
      * @return string HTML string.
      */
-    public static function formatUrl(string $url, array $params, array $args, array $slugParamArg = []): string
-    {
+    public static function formatUrl(
+        string $url,
+        array $params,
+        array $args,
+        array $slugParamArg = [],
+        array $optionalParams = []
+    ): string {
         if ($slugParamArg) {
             $slug = array_values($slugParamArg)[0];
 
@@ -179,34 +195,67 @@ public static function formatUrl(string $url, array $params, array $args, array
             }
         }
 
+        $queryArgs = [];
         if ($params && $args) {
             $queryArgs = self::intersectArgs($args, $params);
-            if ($queryArgs) {
-                $url = self::setUrlQueryArgs($url, $queryArgs);
+        }
+        if ($optionalParams) {
+            foreach ($optionalParams as $k => $v) {
+                if (isset($args[$k])) {
+                    $queryArgs[$k] = $args[$k];
+                } elseif ($v) {
+                    $queryArgs[$k] = $v;
+                }
             }
         }
 
+        if ($queryArgs) {
+            $url = self::setUrlQueryArgs($url, $queryArgs);
+        }
+
         return $url;
     }
 
     /**
      * Formats the given code arguments into a code string.
      *
-     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/0831b937a8468e0f74bd79edd5a59fa8b2e6e763/src/utils/index.ts#L48
+     * @see https://github.com/GoogleChromeLabs/third-party-capital/blob/54cd44d1bd197a7809ab2f6ede4d13a973087c3d/src/utils/index.ts#L52
      *
-     * @param string               $code Code string with placeholders for URL query parameters.
-     * @param array<string, mixed> $args Input arguments for the src attribute query parameters.
+     * @param string               $code           Code string with placeholders for URL query parameters.
+     * @param array<string, mixed> $args           Input arguments for the src attribute query parameters.
+     * @param array<string, mixed> $optionalParams Optional. Optional parameter names and their defaults.
+     *                                             Default empty array.
      * @return string HTML string.
      */
-    public static function formatCode(string $code, array $args): string
-    {
+    public static function formatCode(
+        string $code,
+        array $args,
+        array $optionalParams = []
+    ): string {
+        // Conditionals.
+        $code = preg_replace_callback(
+            '/{{#([^{}]+?)}}(.*){{\/\1}}/',
+            static function ($matches) use ($args, $optionalParams) {
+                if ((isset($args[ $matches[1] ]) && $args[ $matches[1] ]) ||
+                    (isset($optionalParams[ $matches[1] ]) &&  $optionalParams[ $matches[1] ])) {
+                    return $matches[2];
+                }
+                return '';
+            },
+            $code
+        );
+
+        // Variables.
         return preg_replace_callback(
             '/{{([^}]+)}}/',
-            static function ($matches) use ($args) {
+            static function ($matches) use ($args, $optionalParams) {
                 if (isset($args[ $matches[1] ])) {
-                    return $args[ $matches[1] ];
+                    return json_encode($args[ $matches[1] ]);
                 }
-                return '';
+                if (isset($optionalParams[ $matches[1] ])) {
+                    return json_encode($optionalParams[ $matches[1] ]);
+                }
+                return '""'; // The same as `json_encode('')`.
             },
             $code
         );
diff --git a/inc/Data/ThirdPartyHtmlAttributes.php b/inc/Data/ThirdPartyHtmlAttributes.php
index 4722934..051d7d9 100644
--- a/inc/Data/ThirdPartyHtmlAttributes.php
+++ b/inc/Data/ThirdPartyHtmlAttributes.php
@@ -9,6 +9,7 @@
 
 namespace GoogleChromeLabs\ThirdPartyCapital\Data;
 
+use GoogleChromeLabs\ThirdPartyCapital\Contracts\Arrayable;
 use GoogleChromeLabs\ThirdPartyCapital\Util\HtmlAttributes;
 
 /**
@@ -22,7 +23,7 @@ class ThirdPartyHtmlAttributes extends HtmlAttributes
      *
      * @param string $name  Attribute name.
      * @param mixed  $value Attribute value.
-     * @return mixed Sanitized attribute value.
+     * @return string|bool|null|Arrayable Sanitized attribute value.
      */
     protected function sanitizeAttr(string $name, $value)
     {
@@ -36,8 +37,8 @@ protected function sanitizeAttr(string $name, $value)
     /**
      * Returns the attribute string for the given attribute name and value.
      *
-     * @param string $name  Attribute name.
-     * @param mixed  $value Attribute value.
+     * @param string                     $name  Attribute name.
+     * @param string|bool|null|Arrayable $value Attribute value.
      * @return string HTML attribute string (starts with a space), or empty string to skip.
      */
     protected function toAttrString(string $name, $value): string
diff --git a/inc/Data/ThirdPartyHtmlData.php b/inc/Data/ThirdPartyHtmlData.php
index d956f7b..182ed7b 100644
--- a/inc/Data/ThirdPartyHtmlData.php
+++ b/inc/Data/ThirdPartyHtmlData.php
@@ -80,9 +80,6 @@ private function validateData(array $htmlData): void
         if (!isset($htmlData['attributes'])) {
             throw new InvalidThirdPartyDataException('Missing HTML attributes.');
         }
-        if (!isset($htmlData['attributes']['src'])) {
-            throw new InvalidThirdPartyDataException('Missing HTML src attribute.');
-        }
     }
 
     /**
diff --git a/inc/Data/ThirdPartyScriptData.php b/inc/Data/ThirdPartyScriptData.php
index 5d6f036..1ed8484 100644
--- a/inc/Data/ThirdPartyScriptData.php
+++ b/inc/Data/ThirdPartyScriptData.php
@@ -76,6 +76,13 @@ class ThirdPartyScriptData implements Arrayable
      */
     private $params;
 
+    /**
+     * Optional parameters for the script and their defaults, if needed.
+     *
+     * @var array<string, mixed>
+     */
+    private $optionalParams;
+
     /**
      * Constructor.
      *
@@ -159,6 +166,16 @@ public function getParams(): array
         return $this->params;
     }
 
+    /**
+     * Gets the optional parameters for the script with their defaults, if needed.
+     *
+     * @return array<string, mixed> Optional parameters for the script, if needed.
+     */
+    public function getOptionalParams(): array
+    {
+        return $this->optionalParams;
+    }
+
     /**
      * Determines whether the script is an external script.
      *
@@ -192,6 +209,9 @@ public function toArray(): array
         if ($this->params) {
             $data['params'] = $this->params;
         }
+        if ($this->optionalParams) {
+            $data['optionalParams'] = $this->optionalParams;
+        }
 
         return $data;
     }
@@ -278,6 +298,7 @@ private function setData(array $scriptData): void
             $this->$field = isset($scriptData[ $field ]) ? (string) $scriptData[ $field ] : '';
         }
 
-        $this->params = isset($scriptData['params']) ? array_map('strval', $scriptData['params']) : [];
+        $this->params         = isset($scriptData['params']) ? array_map('strval', $scriptData['params']) : [];
+        $this->optionalParams = isset($scriptData['optionalParams']) ? (array) $scriptData['optionalParams'] : [];
     }
 }
diff --git a/inc/ThirdParties/GoogleTagManager.php b/inc/ThirdParties/GoogleTagManager.php
new file mode 100644
index 0000000..19d66a5
--- /dev/null
+++ b/inc/ThirdParties/GoogleTagManager.php
@@ -0,0 +1,29 @@
+<?php
+/**
+ * Class GoogleChromeLabs\ThirdPartyCapital\ThirdParties\GoogleTagManager
+ *
+ * @package   GoogleChromeLabs/ThirdPartyCapital
+ * @copyright 2024 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ */
+
+namespace GoogleChromeLabs\ThirdPartyCapital\ThirdParties;
+
+use GoogleChromeLabs\ThirdPartyCapital\Util\JsonDir;
+
+/**
+ * Class representing the Google Tag Manager integration.
+ */
+class GoogleTagManager extends ThirdPartyBase
+{
+
+    /**
+     * Gets the path to the third party data JSON file.
+     *
+     * @return string Absolute path to the JSON file.
+     */
+    protected function getJsonFilePath(): string
+    {
+        return JsonDir::getFilePath('google-tag-manager.json');
+    }
+}
diff --git a/inc/ThirdParties/ThirdPartyBase.php b/inc/ThirdParties/ThirdPartyBase.php
index fa031b2..71e2195 100644
--- a/inc/ThirdParties/ThirdPartyBase.php
+++ b/inc/ThirdParties/ThirdPartyBase.php
@@ -53,7 +53,7 @@ abstract class ThirdPartyBase implements ThirdParty
      *
      * @param array<string, mixed> $args Input arguments to set.
      */
-    public function __construct(array $args)
+    final public function __construct(array $args)
     {
         $this->jsonFilePath = $this->getJsonFilePath();
 
@@ -65,7 +65,7 @@ public function __construct(array $args)
      *
      * @return string Third party identifier.
      */
-    public function getId(): string
+    final public function getId(): string
     {
         $this->lazilyInitialize();
 
@@ -77,7 +77,7 @@ public function getId(): string
      *
      * @param array<string, mixed> $args Input arguments to set.
      */
-    public function setArgs(array $args): void
+    final public function setArgs(array $args): void
     {
         $this->args = $args;
 
@@ -92,7 +92,7 @@ public function setArgs(array $args): void
      *
      * @return string HTML output, or empty string if not applicable.
      */
-    public function getHtml(): string
+    final public function getHtml(): string
     {
         $this->lazilyInitialize();
 
@@ -106,7 +106,7 @@ public function getHtml(): string
      *
      * @return string[] List of stylesheet URLs, or empty array if not applicable.
      */
-    public function getStylesheets(): array
+    final public function getStylesheets(): array
     {
         $this->lazilyInitialize();
 
@@ -120,7 +120,7 @@ public function getStylesheets(): array
      *
      * @return ThirdPartyScriptOutput[] List of script definition objects, or empty array if not applicable.
      */
-    public function getScripts(): array
+    final public function getScripts(): array
     {
         $this->lazilyInitialize();
 
diff --git a/inc/Util/HtmlAttributes.php b/inc/Util/HtmlAttributes.php
index cb6ce05..2b9d953 100644
--- a/inc/Util/HtmlAttributes.php
+++ b/inc/Util/HtmlAttributes.php
@@ -19,8 +19,8 @@
 /**
  * Class representing a set of HTML Attributes.
  *
- * @implements ArrayAccess<string, string|bool|Arrayable>
- * @implements IteratorAggregate<string, string|bool|Arrayable>
+ * @implements ArrayAccess<string, string|bool|null|Arrayable>
+ * @implements IteratorAggregate<string, string|bool|null|Arrayable>
  */
 class HtmlAttributes implements Arrayable, ArrayAccess, IteratorAggregate
 {
@@ -28,7 +28,7 @@ class HtmlAttributes implements Arrayable, ArrayAccess, IteratorAggregate
     /**
      * Internal attributes storage.
      *
-     * @var array<string, string|bool|Arrayable>
+     * @var array<string, string|bool|null|Arrayable>
      */
     private $attr = [];
 
@@ -64,7 +64,7 @@ public function offsetExists($name)
      * @since n.e.x.t
      *
      * @param string $name Attribute name.
-     * @return mixed Value for the given attribute.
+     * @return string|bool|null|Arrayable Value for the given attribute.
      *
      * @throws NotFoundException Thrown if the attribute is not set.
      */
@@ -115,7 +115,7 @@ public function offsetUnset($name)
      *
      * @since n.e.x.t
      *
-     * @return ArrayIterator<string, string|bool|Arrayable> Attributes iterator.
+     * @return ArrayIterator<string, string|bool|null|Arrayable> Attributes iterator.
      */
     public function getIterator(): Traversable
     {
@@ -159,11 +159,11 @@ public function __toString(): string
      *
      * @param string $name  Attribute name.
      * @param mixed  $value Attribute value.
-     * @return mixed Sanitized attribute value.
+     * @return string|bool|null|Arrayable Sanitized attribute value.
      */
     protected function sanitizeAttr(string $name, $value)
     {
-        if (is_bool($value)) {
+        if (is_bool($value) || is_null($value)) {
             return $value;
         }
         return (string) $value;
@@ -172,12 +172,16 @@ protected function sanitizeAttr(string $name, $value)
     /**
      * Returns the attribute string for the given attribute name and value.
      *
-     * @param string $name  Attribute name.
-     * @param mixed  $value Attribute value.
+     * @param string                     $name  Attribute name.
+     * @param string|bool|null|Arrayable $value Attribute value.
      * @return string HTML attribute string (starts with a space), or empty string to skip.
      */
     protected function toAttrString(string $name, $value): string
     {
+        if (is_null($value)) {
+            return '';
+        }
+
         if (is_bool($value)) {
             return $value ? ' ' . $name : '';
         }
diff --git a/src/utils/index.test.ts b/src/utils/index.test.ts
index dfd0185..dd6a2f1 100644
--- a/src/utils/index.test.ts
+++ b/src/utils/index.test.ts
@@ -328,7 +328,7 @@ describe('Utils', () => {
         params: {
           val: null,
         },
-        output: `null`,
+        output: `undefined`,
       },
       // undefined
       {
@@ -343,6 +343,46 @@ describe('Utils', () => {
         },
         output: `{"key":"value"}`,
       },
+      // conditional with true
+      {
+        input: '{{#enabled}}window.func("enable", true);{{/enabled}}',
+        params: {
+          enabled: true,
+        },
+        output: `window.func("enable", true);`,
+      },
+      // conditional with false
+      {
+        input: '{{#enabled}}window.func("enable", true);{{/enabled}}',
+        params: {
+          enabled: false,
+        },
+        output: ``,
+      },
+      // conditional with true including variable
+      {
+        input: '{{#name}}window.func("setName", {{name}});{{/name}}',
+        params: {
+          name: 'James',
+        },
+        output: `window.func("setName", "James");`,
+      },
+      // conditional with false including variable
+      {
+        input: '{{#name}}window.func("setName", {{name}});{{/name}}',
+        params: {
+          name: null,
+        },
+        output: ``,
+      },
+      // conditional with too many braces (do not do that!)
+      {
+        input: '{{{#name}}}window.func("setName", {{name}});{{{/name}}}',
+        params: {
+          name: 'James',
+        },
+        output: `{}window.func("setName", "James");{}`,
+      },
     ];
 
     it.each(inputs)(
diff --git a/src/utils/index.ts b/src/utils/index.ts
index 2834526..78ac1a2 100644
--- a/src/utils/index.ts
+++ b/src/utils/index.ts
@@ -40,8 +40,14 @@ export function formatUrl(
   if (params && args) {
     params.forEach((param: string) => {
       if (args[param]) newUrl.searchParams.set(param, args[param]);
-      else if (optionalParams?.[param]) {
-        newUrl.searchParams.set(param, optionalParams?.[param]);
+    });
+  }
+
+  if (optionalParams) {
+    Object.keys(optionalParams).forEach((key: string) => {
+      if (args?.[key]) newUrl.searchParams.set(key, args[key]);
+      else if (optionalParams[key]) {
+        newUrl.searchParams.set(key, optionalParams[key]);
       }
     });
   }
@@ -54,11 +60,22 @@ export function formatCode(
   args?: Inputs,
   optionalParams?: Inputs,
 ) {
-  return code.replace(/{{(.*?)}}/g, (match) => {
+  // Conditionals.
+  code = code.replace(
+    /{{#([^{}]+?)}}(.*){{\/\1}}/g,
+    (match, name, innerCode) => {
+      if (args?.[name] || optionalParams?.[name]) {
+        return innerCode;
+      }
+      return '';
+    },
+  );
+
+  // Variable replacements.
+  return code.replace(/{{[^#/](.*?)}}/g, (match) => {
     const name = match.split(/{{|}}/).filter(Boolean)[0];
-    return JSON.stringify(
-      args?.[name] !== undefined ? args?.[name] : optionalParams?.[name],
-    );
+
+    return JSON.stringify(args?.[name] ?? optionalParams?.[name] ?? undefined);
   });
 }
 
@@ -157,19 +174,15 @@ export function formatData(data: Data, args: Inputs): Output {
                 ...script,
                 url: formatUrl(
                   script.url,
-                  allScriptParams,
-                  scriptUrlParamInputs,
+                  script.params,
+                  args,
                   undefined,
                   script.optionalParams,
                 ),
               }
             : {
                 ...script,
-                code: formatCode(
-                  script.code,
-                  scriptUrlParamInputs,
-                  script.optionalParams,
-                ),
+                code: formatCode(script.code, args, script.optionalParams),
               };
         })
       : undefined,
diff --git a/tests/phpunit/tests/Data/ThirdPartyDataFormatterTest.php b/tests/phpunit/tests/Data/ThirdPartyDataFormatterTest.php
index f5a4719..c901b7c 100644
--- a/tests/phpunit/tests/Data/ThirdPartyDataFormatterTest.php
+++ b/tests/phpunit/tests/Data/ThirdPartyDataFormatterTest.php
@@ -333,11 +333,11 @@ public function testFormatUrlWithQueryAndSlugParamAndParamsAndArgs()
     public function testFormatCodeWithoutArgs()
     {
         $code = ThirdPartyDataFormatter::formatCode(
-            'document.querySelector("{{selector}}").addEventListener(api.{{callback}});',
+            'document.querySelector({{selector}}).addEventListener(api[{{callback}}]);',
             []
         );
         $this->assertSame(
-            'document.querySelector("").addEventListener(api.);',
+            'document.querySelector("").addEventListener(api[""]);',
             $code
         );
     }
@@ -345,14 +345,14 @@ public function testFormatCodeWithoutArgs()
     public function testFormatCodeWithArgs()
     {
         $code = ThirdPartyDataFormatter::formatCode(
-            'document.querySelector("{{selector}}").addEventListener(api.{{callback}});',
+            'document.querySelector({{selector}}).addEventListener(api[{{callback}}]);',
             [
                 'selector' => '.my-cta-button',
                 'callback' => 'addToCart',
             ]
         );
         $this->assertSame(
-            'document.querySelector(".my-cta-button").addEventListener(api.addToCart);',
+            'document.querySelector(".my-cta-button").addEventListener(api["addToCart"]);',
             $code
         );
     }
@@ -360,7 +360,7 @@ public function testFormatCodeWithArgs()
     public function testFormatCodeWithArgsIncorrectOrderAndTooMany()
     {
         $code = ThirdPartyDataFormatter::formatCode(
-            'document.querySelector("{{selector}}").addEventListener(api.{{callback}});',
+            'document.querySelector({{selector}}).addEventListener(api[{{callback}}]);',
             [
                 'callback' => 'addToCart',
                 'device'   => 'phone',
@@ -368,8 +368,48 @@ public function testFormatCodeWithArgsIncorrectOrderAndTooMany()
             ]
         );
         $this->assertSame(
-            'document.querySelector(".my-cta-button").addEventListener(api.addToCart);',
+            'document.querySelector(".my-cta-button").addEventListener(api["addToCart"]);',
             $code
         );
     }
+
+    /**
+     * @dataProvider dataFormatCodeWithConditionals
+     */
+    public function testFormatCodeWithConditionals(string $input, array $params, string $expected)
+    {
+        $code = ThirdPartyDataFormatter::formatCode($input, $params);
+        $this->assertSame($expected, $code);
+    }
+
+    public function dataFormatCodeWithConditionals(): array
+    {
+        return [
+            'true'                => [
+                '{{#enabled}}window.func("enable", true);{{/enabled}}',
+                [ 'enabled' => true ],
+                'window.func("enable", true);',
+            ],
+            'false'               => [
+                '{{#enabled}}window.func("enable", true);{{/enabled}}',
+                [ 'enabled' => false ],
+                '',
+            ],
+            'true with variable'  => [
+                '{{#name}}window.func("setName", {{name}});{{/name}}',
+                [ 'name' => 'James' ],
+                'window.func("setName", "James");',
+            ],
+            'false with variable' => [
+                '{{#name}}window.func("setName", {{name}});{{/name}}',
+                [ 'name' => null ],
+                '',
+            ],
+            'too many braces' => [
+                '{{{#name}}}window.func("setName", {{name}});{{{/name}}}',
+                [ 'name' => 'James' ],
+                '{}window.func("setName", "James");{}',
+            ],
+        ];
+    }
 }
diff --git a/tests/phpunit/tests/ThirdParties/GoogleAnalyticsTest.php b/tests/phpunit/tests/ThirdParties/GoogleAnalyticsTest.php
new file mode 100644
index 0000000..a8c801d
--- /dev/null
+++ b/tests/phpunit/tests/ThirdParties/GoogleAnalyticsTest.php
@@ -0,0 +1,145 @@
+<?php
+/**
+ * Tests for GoogleChromeLabs\ThirdPartyCapital\ThirdParties\GoogleAnalytics
+ *
+ * @package   GoogleChromeLabs/ThirdPartyCapital
+ * @copyright 2024 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ */
+
+namespace GoogleChromeLabs\ThirdPartyCapital\Tests;
+
+use GoogleChromeLabs\ThirdPartyCapital\Data\ThirdPartyScriptData;
+use GoogleChromeLabs\ThirdPartyCapital\TestUtils\TestCase;
+use GoogleChromeLabs\ThirdPartyCapital\ThirdParties\GoogleAnalytics;
+
+class GoogleAnalyticsTest extends TestCase
+{
+
+    /**
+     * Tests the output data for Google Analytics.
+     *
+     * This is effectively an integration test to ensure the JSON schema is handled correctly.
+     *
+     * @dataProvider dataOutput
+     */
+    public function testOutput(array $args, array $expectedScripts)
+    {
+        $ga = new GoogleAnalytics($args);
+        $this->assertSame('google-analytics', $ga->getId());
+        $this->assertSame('', $ga->getHtml());
+        $this->assertSame([], $ga->getStylesheets());
+        $this->assertSame(
+            $expectedScripts,
+            array_map(
+                static function ($script) {
+                    return $script->toArray();
+                },
+                $ga->getScripts()
+            )
+        );
+    }
+
+    public function dataOutput(): array
+    {
+        return [
+            'basic example'          => [
+                [ 'id' => 'G-12345678' ],
+                [
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'url'      => 'https://www.googletagmanager.com/gtag/js?id=G-12345678',
+                        'key'      => 'gtag',
+                    ],
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'code'     => "window[\"dataLayer\"]=window[\"dataLayer\"]||[];window['gtag-'+\"dataLayer\"]=function (){window[\"dataLayer\"].push(arguments);};window['gtag-'+\"dataLayer\"]('js',new Date());window['gtag-'+\"dataLayer\"]('config',\"G-12345678\")",
+                        'key'      => 'setup',
+                    ],
+                ],
+            ],
+            'with custom data layer' => [
+                [
+                    'id' => 'G-13579',
+                    'l'  => 'myDataLayer1',
+                ],
+                [
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'url'      => 'https://www.googletagmanager.com/gtag/js?id=G-13579&l=myDataLayer1',
+                        'key'      => 'gtag',
+                    ],
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'code'     => "window[\"myDataLayer1\"]=window[\"myDataLayer1\"]||[];window['gtag-'+\"myDataLayer1\"]=function (){window[\"myDataLayer1\"].push(arguments);};window['gtag-'+\"myDataLayer1\"]('js',new Date());window['gtag-'+\"myDataLayer1\"]('config',\"G-13579\")",
+                        'key'      => 'setup',
+                    ],
+                ],
+            ],
+            'with default consent'   => [
+                [
+                    'id'            => 'G-12345678',
+                    'consentValues' => [
+                        'ad_user_data'        => 'denied',
+                        'ad_personalization'  => 'denied',
+                        'ad_storage'          => 'denied',
+                        'analytics_storage'   => 'denied',
+                        'wait_for_update'     => 500,
+                    ],
+                ],
+                [
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'url'      => 'https://www.googletagmanager.com/gtag/js?id=G-12345678',
+                        'key'      => 'gtag',
+                    ],
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'code'     => "window[\"dataLayer\"]=window[\"dataLayer\"]||[];window['gtag-'+\"dataLayer\"]=function (){window[\"dataLayer\"].push(arguments);};window['gtag-'+\"dataLayer\"]('consent', \"default\", {\"ad_user_data\":\"denied\",\"ad_personalization\":\"denied\",\"ad_storage\":\"denied\",\"analytics_storage\":\"denied\",\"wait_for_update\":500});window['gtag-'+\"dataLayer\"]('js',new Date());window['gtag-'+\"dataLayer\"]('config',\"G-12345678\")",
+                        'key'      => 'setup',
+                    ],
+                ],
+            ],
+            'with consent update'    => [
+                [
+                    'id'            => 'G-12345678',
+                    'consentType'   => 'update',
+                    'consentValues' => [
+                        'ad_user_data'        => 'granted',
+                        'ad_personalization'  => 'granted',
+                        'ad_storage'          => 'granted',
+                        'analytics_storage'   => 'granted',
+                    ],
+                ],
+                [
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'url'      => 'https://www.googletagmanager.com/gtag/js?id=G-12345678',
+                        'key'      => 'gtag',
+                    ],
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'code'     => "window[\"dataLayer\"]=window[\"dataLayer\"]||[];window['gtag-'+\"dataLayer\"]=function (){window[\"dataLayer\"].push(arguments);};window['gtag-'+\"dataLayer\"]('consent', \"update\", {\"ad_user_data\":\"granted\",\"ad_personalization\":\"granted\",\"ad_storage\":\"granted\",\"analytics_storage\":\"granted\"});window['gtag-'+\"dataLayer\"]('js',new Date());window['gtag-'+\"dataLayer\"]('config',\"G-12345678\")",
+                        'key'      => 'setup',
+                    ],
+                ],
+            ],
+        ];
+    }
+}
diff --git a/tests/phpunit/tests/ThirdParties/GoogleMapsEmbedTest.php b/tests/phpunit/tests/ThirdParties/GoogleMapsEmbedTest.php
new file mode 100644
index 0000000..ea7ea03
--- /dev/null
+++ b/tests/phpunit/tests/ThirdParties/GoogleMapsEmbedTest.php
@@ -0,0 +1,75 @@
+<?php
+/**
+ * Tests for GoogleChromeLabs\ThirdPartyCapital\ThirdParties\GoogleMapsEmbed
+ *
+ * @package   GoogleChromeLabs/ThirdPartyCapital
+ * @copyright 2024 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ */
+
+namespace GoogleChromeLabs\ThirdPartyCapital\Tests;
+
+use GoogleChromeLabs\ThirdPartyCapital\TestUtils\TestCase;
+use GoogleChromeLabs\ThirdPartyCapital\ThirdParties\GoogleMapsEmbed;
+
+class GoogleMapsEmbedTest extends TestCase
+{
+
+    /**
+     * Tests the output data for Google Maps Embed.
+     *
+     * This is effectively an integration test to ensure the JSON schema is handled correctly.
+     *
+     * @dataProvider dataOutput
+     */
+    public function testOutput(array $args, string $expectedHtml)
+    {
+        $gme = new GoogleMapsEmbed($args);
+        $this->assertSame('google-maps-embed', $gme->getId());
+        $this->assertSame($expectedHtml, $gme->getHtml());
+        $this->assertSame([], $gme->getStylesheets());
+        $this->assertSame([], $gme->getScripts());
+    }
+
+    public function dataOutput(): array
+    {
+        return [
+            'basic example'    => [
+                [
+                    'key' => 'MY_API_KEY',
+                    'q'   => 'Space Needle, Seattle WA',
+                ],
+                $this->getHtmlString(
+                    'iframe',
+                    [
+                        'loading'         => 'lazy',
+                        'src'             => 'https://www.google.com/maps/embed/v1/place?key=MY_API_KEY&q=Space+Needle%2C+Seattle+WA',
+                        'referrerpolicy'  => 'no-referrer-when-downgrade',
+                        'frameborder'     => '0',
+                        'style'           => 'border:0',
+                        'allowfullscreen' => true,
+                    ]
+                ),
+            ],
+            'with custom mode' => [
+                [
+                    'mode'    => 'search',
+                    'key'     => 'MY_API_KEY',
+                    'q'       => 'tourist attractions in Seattle',
+                    'maptype' => 'satellite',
+                ],
+                $this->getHtmlString(
+                    'iframe',
+                    [
+                        'loading'         => 'lazy',
+                        'src'             => 'https://www.google.com/maps/embed/v1/search?key=MY_API_KEY&q=tourist+attractions+in+Seattle&maptype=satellite',
+                        'referrerpolicy'  => 'no-referrer-when-downgrade',
+                        'frameborder'     => '0',
+                        'style'           => 'border:0',
+                        'allowfullscreen' => true,
+                    ]
+                ),
+            ],
+        ];
+    }
+}
diff --git a/tests/phpunit/tests/ThirdParties/GoogleTagManagerTest.php b/tests/phpunit/tests/ThirdParties/GoogleTagManagerTest.php
new file mode 100644
index 0000000..aec448d
--- /dev/null
+++ b/tests/phpunit/tests/ThirdParties/GoogleTagManagerTest.php
@@ -0,0 +1,89 @@
+<?php
+/**
+ * Tests for GoogleChromeLabs\ThirdPartyCapital\ThirdParties\GoogleTagManager
+ *
+ * @package   GoogleChromeLabs/ThirdPartyCapital
+ * @copyright 2024 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ */
+
+namespace GoogleChromeLabs\ThirdPartyCapital\Tests;
+
+use GoogleChromeLabs\ThirdPartyCapital\Data\ThirdPartyScriptData;
+use GoogleChromeLabs\ThirdPartyCapital\TestUtils\TestCase;
+use GoogleChromeLabs\ThirdPartyCapital\ThirdParties\GoogleTagManager;
+
+class GoogleTagManagerTest extends TestCase
+{
+
+    /**
+     * Tests the output data for Google Tag Manager.
+     *
+     * This is effectively an integration test to ensure the JSON schema is handled correctly.
+     *
+     * @dataProvider dataOutput
+     */
+    public function testOutput(array $args, array $expectedScripts)
+    {
+        $gtm = new GoogleTagManager($args);
+        $this->assertSame('google-tag-manager', $gtm->getId());
+        $this->assertSame('', $gtm->getHtml());
+        $this->assertSame([], $gtm->getStylesheets());
+        $this->assertSame(
+            $expectedScripts,
+            array_map(
+                static function ($script) {
+                    return $script->toArray();
+                },
+                $gtm->getScripts()
+            )
+        );
+    }
+
+    public function dataOutput(): array
+    {
+        return [
+            'basic example'          => [
+                [ 'id' => 'GTM-12345678' ],
+                [
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'url'      => 'https://www.googletagmanager.com/gtm.js?id=GTM-12345678',
+                        'key'      => 'gtm',
+                    ],
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'code'     => "window[\"dataLayer\"]=window[\"dataLayer\"]||[];window[\"dataLayer\"].push({'gtm.start':new Date().getTime(),event:'gtm.js'});",
+                        'key'      => 'setup',
+                    ],
+                ],
+            ],
+            'with custom data layer' => [
+                [
+                    'id' => 'GTM-A1B2C3',
+                    'l'  => 'myDataLayer1',
+                ],
+                [
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'url'      => 'https://www.googletagmanager.com/gtm.js?id=GTM-A1B2C3&l=myDataLayer1',
+                        'key'      => 'gtm',
+                    ],
+                    [
+                        'strategy' => ThirdPartyScriptData::STRATEGY_WORKER,
+                        'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                        'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                        'code'     => "window[\"myDataLayer1\"]=window[\"myDataLayer1\"]||[];window[\"myDataLayer1\"].push({'gtm.start':new Date().getTime(),event:'gtm.js'});",
+                        'key'      => 'setup',
+                    ],
+                ],
+            ],
+        ];
+    }
+}
diff --git a/tests/phpunit/tests/ThirdParties/YouTubeEmbedTest.php b/tests/phpunit/tests/ThirdParties/YouTubeEmbedTest.php
new file mode 100644
index 0000000..67cc12e
--- /dev/null
+++ b/tests/phpunit/tests/ThirdParties/YouTubeEmbedTest.php
@@ -0,0 +1,72 @@
+<?php
+/**
+ * Tests for GoogleChromeLabs\ThirdPartyCapital\ThirdParties\YouTubeEmbed
+ *
+ * @package   GoogleChromeLabs/ThirdPartyCapital
+ * @copyright 2024 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ */
+
+namespace GoogleChromeLabs\ThirdPartyCapital\Tests;
+
+use GoogleChromeLabs\ThirdPartyCapital\Data\ThirdPartyScriptData;
+use GoogleChromeLabs\ThirdPartyCapital\TestUtils\TestCase;
+use GoogleChromeLabs\ThirdPartyCapital\ThirdParties\YouTubeEmbed;
+
+class YouTubeEmbedTest extends TestCase
+{
+
+    /**
+     * Tests the output data for YouTube Embed.
+     *
+     * This is effectively an integration test to ensure the JSON schema is handled correctly.
+     *
+     * @dataProvider dataOutput
+     */
+    public function testOutput(array $args, string $expectedHtml)
+    {
+        $yte = new YouTubeEmbed($args);
+        $this->assertSame('youtube-embed', $yte->getId());
+        $this->assertSame($expectedHtml, $yte->getHtml());
+        $this->assertSame(
+            ['https://cdn.jsdelivr.net/gh/paulirish/lite-youtube-embed@master/src/lite-yt-embed.css'],
+            $yte->getStylesheets()
+        );
+        $this->assertSame(
+            [
+                [
+                    'strategy' => ThirdPartyScriptData::STRATEGY_IDLE,
+                    'location' => ThirdPartyScriptData::LOCATION_HEAD,
+                    'action'   => ThirdPartyScriptData::ACTION_APPEND,
+                    'url'      => 'https://cdn.jsdelivr.net/gh/paulirish/lite-youtube-embed@master/src/lite-yt-embed.js',
+                    'key'      => 'lite-yt-embed',
+                ],
+            ],
+            array_map(
+                static function ($script) {
+                    return $script->toArray();
+                },
+                $yte->getScripts()
+            )
+        );
+    }
+
+    public function dataOutput(): array
+    {
+        return [
+            'basic example'    => [
+                [
+                    'videoid'   => 'ogfYd705cRs',
+                    'playlabel' => 'Play: Keynote (Google I/O 2018)',
+                ],
+                $this->getHtmlString(
+                    'lite-youtube',
+                    [
+                        'videoid'   => 'ogfYd705cRs',
+                        'playlabel' => 'Play: Keynote (Google I/O 2018)',
+                    ]
+                ),
+            ],
+        ];
+    }
+}
diff --git a/tests/phpunit/tests/Util/HtmlAttributesTest.php b/tests/phpunit/tests/Util/HtmlAttributesTest.php
index 7e039f1..5338537 100644
--- a/tests/phpunit/tests/Util/HtmlAttributesTest.php
+++ b/tests/phpunit/tests/Util/HtmlAttributesTest.php
@@ -140,6 +140,15 @@ public function dataToString()
                 ],
                 ' id="unique-id" async class="demo-class"',
             ],
+            'with null'          => [
+                [
+                    'id'     => 'some-id',
+                    'width'  => null,
+                    'height' => null,
+                    'class'  => 'demo-class',
+                ],
+                ' id="some-id" class="demo-class"',
+            ],
         ];
     }
 }
diff --git a/tests/phpunit/utils/TestCase.php b/tests/phpunit/utils/TestCase.php
index 0cfebcb..285bf7b 100644
--- a/tests/phpunit/utils/TestCase.php
+++ b/tests/phpunit/utils/TestCase.php
@@ -16,6 +16,28 @@
 abstract class TestCase extends PHPUnitTestCase
 {
 
+    /**
+     * Test helper to turn a HTML element name and attributes array into a string.
+     *
+     * @param string                     $element    HTML element name.
+     * @param array<string, string|bool> $attributes Associative array of HTML attributes.
+     * @return string The resulting HTML string.
+     */
+    protected function getHtmlString(string $element, array $attributes): string
+    {
+        $attr_string = '';
+        foreach ($attributes as $key => $value) {
+            if (is_bool($value)) {
+                if ($value) {
+                    $attr_string .= ' ' . $key;
+                }
+                continue;
+            }
+            $attr_string .= ' ' . $key . '="' . $value . '"';
+        }
+        return '<' . $element . $attr_string . '></' . $element . '>';
+    }
+
     protected function runGetterTestCase(string $className, string $getMethod, array $args, $expected)
     {
         if (is_subclass_of($expected, Exception::class)) {