✅ Added Tests for EnvironmentBasedModelMapper (#422)

While working to confirm that the logic in codemodder-java and the
platform is in sync, I found opportunities to add missing tests and fix
some pitfalls.

/towards #work

plugins/codemodder-plugin-llm/src/main/java/io/codemodder/plugins/llm/EnvironmentBasedModelMapper.java

@@ -1,22 +1,34 @@
 package io.codemodder.plugins.llm;
 
 import java.util.HashMap;
+import java.util.Map;
 
 /** Mapper that maps models to their deployment names based on environment variables. */
 final class EnvironmentBasedModelMapper implements ModelMapper {
-  private static final String DEPLOYMENT_TEMPLATE = "CODEMODDER_AZURE_OPENAI_%s_DEPLOYMENT";
 
   private final HashMap<Model, String> map = new HashMap<>();
 
   EnvironmentBasedModelMapper() {
-    for (Model m : StandardModel.values()) {
-      final var deployment = System.getenv(String.format(DEPLOYMENT_TEMPLATE, m));
-      map.put(m, deployment == null ? m.id() : deployment);
+    this(System.getenv());
+  }
+
+  EnvironmentBasedModelMapper(final Map<String, String> environment) {
+    for (final Model model : StandardModel.values()) {
+      final var name = String.format(DEPLOYMENT_TEMPLATE, toEnvironmentVariableCase(model.id()));
+      final var deployment = environment.getOrDefault(name, model.id());
+      map.put(model, deployment);
     }
   }
 
   @Override
   public String getModelName(Model model) {
-    return map.get(model);
+    return map.getOrDefault(model, model.id());
   }
+
+  /** Converts a model ID to environment variable casing. */
+  private static String toEnvironmentVariableCase(String input) {
+    return input.toUpperCase().replace('-', '_').replace('.', '_');
+  }
+
+  private static final String DEPLOYMENT_TEMPLATE = "CODEMODDER_AZURE_OPENAI_%s_DEPLOYMENT";
 }

plugins/codemodder-plugin-llm/src/test/java/io/codemodder/plugins/llm/EnvironmentBasedModelMapperTest.java

@@ -0,0 +1,62 @@
+package io.codemodder.plugins.llm;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.mockito.Mockito.withSettings;
+
+import java.util.Map;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.EnumSource;
+
+/** Unit tests for {@link EnvironmentBasedModelMapper}. */
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+final class EnvironmentBasedModelMapperTest {
+
+  private EnvironmentBasedModelMapper mapper;
+
+  @BeforeAll
+  void before() {
+    final var environment =
+        Map.of(
+            "CODEMODDER_AZURE_OPENAI_GPT_3_5_TURBO_0125_DEPLOYMENT",
+            "my-gpt-3.5-turbo",
+            "CODEMODDER_AZURE_OPENAI_GPT_4_0613_DEPLOYMENT",
+            "my-gpt-4",
+            "CODEMODDER_AZURE_OPENAI_GPT_4_TURBO_2024_04_09_DEPLOYMENT",
+            "my-gpt-4-turbo",
+            "CODEMODDER_AZURE_OPENAI_GPT_4O_2024_05_13_DEPLOYMENT",
+            "my-gpt-4o");
+    mapper = new EnvironmentBasedModelMapper(environment);
+  }
+
+  /** Spot checks one of the standard models to make sure the mapping works as expected */
+  @Test
+  void it_maps_model_name_to_deployment() {
+    final var name = mapper.getModelName(StandardModel.GPT_3_5_TURBO_0125);
+    assertThat(name).isEqualTo("my-gpt-3.5-turbo");
+  }
+
+  /**
+   * This is a meta-test that fails when we add a new standard model but forget to update the
+   * mapping in {@link #before()} to ensure that all standard models are covered.
+   */
+  @EnumSource(StandardModel.class)
+  @ParameterizedTest
+  void it_looks_up_all_standard_models(final Model model) {
+    final var name = mapper.getModelName(model);
+    assertThat(name).isNotEqualTo(model.id()).startsWith("my-gpt");
+  }
+
+  @Test
+  void it_returns_model_id_when_no_mapping_exists() {
+    // GIVEN some model that doesn't have a mapping
+    final var model = mock(Model.class, withSettings().stubOnly());
+    when(model.id()).thenReturn("test");
+    final var name = mapper.getModelName(model);
+    assertThat(name).isEqualTo(model.id());
+  }
+}