diff --git a/src/test/java/lambdas/FileFilterTest.java b/src/test/java/lambdas/FileFilterTest.java
new file mode 100644
index 0000000..eb81181
--- /dev/null
+++ b/src/test/java/lambdas/FileFilterTest.java
@@ -0,0 +1,72 @@
+package lambdas;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.io.FileFilter;
+
+import static java.util.Map.*;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class FileFilterTest {
+    private final File root = new File("src/main/java");
+
+    @Test
+    void listFiles() {
+        File[] files = root.listFiles();
+        assert files != null;
+        assertThat(files.length).isEqualTo(22);
+    }
+
+    @Test
+    void listDirectories_anonInnerClass() {
+        File[] directories = root.listFiles(new java.io.FileFilter() {
+            @Override
+            public boolean accept(File file) {
+                return file.isDirectory();
+            }
+        });
+        assert directories != null;
+        assertThat(directories.length).isEqualTo(14);
+    }
+
+    @Test
+    void listDirectories_expressionLambda() {
+        File[] directories = root.listFiles(file -> file.isDirectory());
+        assert directories != null;
+        assertThat(directories.length).isEqualTo(14);
+    }
+
+    @Test
+    void listJavaSrcFiles_fileFilter() {
+        File[] javaSrcFiles = root.listFiles(file -> file.getName()
+                .endsWith(".java"));
+        assert javaSrcFiles != null;
+        assertThat(javaSrcFiles.length).isEqualTo(8);
+    }
+
+    @Test
+    void listJavaSrcFiles_fileNameFilter() {
+        File[] javaSrcFiles = root.listFiles((File dir, String name) -> name.endsWith(".java"));
+        assert javaSrcFiles != null;
+        assertThat(javaSrcFiles.length).isEqualTo(8);
+    }
+
+    @Test
+    void listJavaSrcFiles_fileFilter_variable() {
+        FileFilter filter = (File file) -> file.getName()
+                .endsWith(".java");
+        File[] javaSrcFiles = root.listFiles(filter);
+        assert javaSrcFiles != null;
+        assertThat(javaSrcFiles.length).isEqualTo(8);
+    }
+
+    @Test
+    void forEachMap() {
+        ofEntries(
+                entry("a", 1),
+                entry("b", 2),
+                entry("c", 2))
+                .forEach((k, v) -> System.out.println(k + " -> " + v));
+    }
+}
diff --git a/src/test/java/lambdas/LazySupplierTest.java b/src/test/java/lambdas/LazySupplierTest.java
new file mode 100644
index 0000000..e2042f3
--- /dev/null
+++ b/src/test/java/lambdas/LazySupplierTest.java
@@ -0,0 +1,35 @@
+package lambdas;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.logging.Logger;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class LazySupplierTest {
+    private final Logger logger = Logger.getLogger(LazySupplierTest.class.getName());
+
+    private String getErrorMessage() {
+        System.out.println("calling getErrorMessage()");
+        return "An error occurred";
+    }
+
+    private String getLogMessage() {
+        System.out.println("calling getLogMessage()");
+        return "log message";
+    }
+
+    @Test
+    void eagerMessages() {
+        boolean condition = true;
+        assertTrue(condition, getErrorMessage());
+        logger.fine(getLogMessage());
+    }
+
+    @Test
+    void lazyMessages() {
+        boolean condition = true;
+        assertTrue(condition, () -> getErrorMessage());
+        logger.fine(() -> getLogMessage());
+    }
+}
diff --git a/src/test/java/lambdas/PredicateTest.java b/src/test/java/lambdas/PredicateTest.java
new file mode 100644
index 0000000..9d3fd07
--- /dev/null
+++ b/src/test/java/lambdas/PredicateTest.java
@@ -0,0 +1,47 @@
+package lambdas;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.function.Predicate;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class PredicateTest {
+
+    @Test
+    void implementPredicateAsAnonInnerClass() {
+        Predicate<String> p = new Predicate<String>() {
+            @Override
+            public boolean test(String s) {
+                return s.length() > 5;
+            }
+        };
+        assertFalse(p.test("Hello"));
+        assertTrue(p.test("Hello World"));
+    }
+
+    @Test
+    void implementPredicateAsExpressionLambda() {
+        Predicate<String> p = s -> s.length() > 5;
+        assertFalse(p.test("Hello"));
+        assertTrue(p.test("Hello World"));
+    }
+
+    @Test
+    void implementPredicateAsBlockLambda() {
+        Predicate<String> p = s -> {
+            System.out.println("Evaluating whether s length > 5: " + s);
+            return s.length() > 5;
+        };
+        assertFalse(p.test("Hello"));
+        assertTrue(p.test("Hello World"));
+    }
+
+    @Test
+    void testRunnable() {
+        Runnable r = () -> System.out.println("Hello World");
+        Thread thread = new Thread(r);
+        thread.start();
+    }
+}