Add comprehensive tests for compose variable substitution feature

Co-authored-by: kiview <[email protected]>

Author: Copilot

core/src/test/java/org/testcontainers/containers/ComposeVariableSubstitutionIntegrationTest.java

@@ -0,0 +1,45 @@
+package org.testcontainers.containers;
+
+import org.junit.Test;
+import org.testcontainers.containers.output.Slf4jLogConsumer;
+
+import java.io.File;
+
+import static org.assertj.core.api.Assertions.assertThatNoException;
+
+/**
+ * Integration test for Docker Compose variable substitution.
+ * Tests the scenario described in the GitHub issue where image names with variables 
+ * like ${TAG_CONFLUENT} were causing warnings.
+ */
+public class ComposeVariableSubstitutionIntegrationTest {
+
+    @Test
+    public void shouldHandleVariableSubstitutionWithoutWarnings() {
+        // Set up environment variable as if it was set by the user
+        System.setProperty("TAG_CONFLUENT", "7.0.0");
+        System.setProperty("REDIS_VERSION", "alpine");
+
+        try {
+            // This should not generate warnings about invalid image names
+            // because variable substitution should resolve ${TAG_CONFLUENT} to 7.0.0
+            assertThatNoException().isThrownBy(() -> {
+                try (ComposeContainer compose = new ComposeContainer(
+                    new File("src/test/resources/docker-compose-variable-substitution.yml")
+                )
+                    .withLocalCompose(true)
+                    .withPull(false)  // Don't actually pull images in test
+                    .withLogConsumer("confluent", new Slf4jLogConsumer(org.slf4j.LoggerFactory.getLogger("confluent-test")))
+                ) {
+                    // Just validate the compose container can be created without exceptions
+                    // The key test is that ParsedDockerComposeFile doesn't throw on variable substitution
+                    // We're not actually starting the containers to avoid requiring Docker in the test
+                }
+            });
+        } finally {
+            // Clean up
+            System.clearProperty("TAG_CONFLUENT");
+            System.clearProperty("REDIS_VERSION");
+        }
+    }
+}

core/src/test/java/org/testcontainers/containers/OriginalIssueDemo.java

@@ -0,0 +1,45 @@
+package org.testcontainers.containers;
+
+import org.junit.Test;
+
+import java.io.File;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Test to demonstrate the fix for the original issue where variable substitution was not working.
+ */  
+public class OriginalIssueDemo {
+
+    @Test
+    public void demonstrateOriginalIssueIsFixed() {
+        // Set the environment variable that was mentioned in the issue
+        System.setProperty("TAG_CONFLUENT", "7.0.0");
+        
+        try {
+            // Parse the compose file that contains the problematic image name
+            ParsedDockerComposeFile parsedFile = new ParsedDockerComposeFile(
+                new File("src/test/resources/docker-compose-variable-substitution.yml")
+            );
+            
+            // Before our fix, this would contain "confluentinc/cp-server:${TAG_CONFLUENT}"
+            // After our fix, this should contain "confluentinc/cp-server:7.0.0"
+            String actualImageName = parsedFile.getServiceNameToImageNames()
+                .get("confluent")
+                .iterator()
+                .next();
+                
+            assertThat(actualImageName)
+                .as("Image name should have variable substituted")
+                .isEqualTo("confluentinc/cp-server:7.0.0")
+                .doesNotContain("${TAG_CONFLUENT}");
+                
+            System.out.println("✅ SUCCESS: Variable substitution is working!");
+            System.out.println("   Original: confluentinc/cp-server:${TAG_CONFLUENT}");
+            System.out.println("   Resolved: " + actualImageName);
+            
+        } finally {
+            System.clearProperty("TAG_CONFLUENT");
+        }
+    }
+}

core/src/test/java/org/testcontainers/containers/ParsedDockerComposeFileValidationTest.java

@@ -231,4 +231,50 @@ public void shouldSubstituteEnvironmentVariablesFromFile() {
             System.clearProperty("REDIS_VERSION");
         }
     }
+
+    @Test
+    public void shouldHandleEdgeCasesInVariableSubstitution() {
+        // Test various edge cases
+        System.setProperty("SIMPLE_VAR", "simple-value");
+        System.setProperty("WITH_SPECIAL_CHARS", "registry.io/app:v1.2.3");
+        System.setProperty("EMPTY_VAR", "");
+
+        try {
+            ParsedDockerComposeFile parsedFile = new ParsedDockerComposeFile(
+                ImmutableMap.of(
+                    "version", "2",
+                    "services", ImmutableMap.of(
+                        // Test $VAR syntax  
+                        "service1", ImmutableMap.of("image", "redis:$SIMPLE_VAR"),
+                        // Test complex image names with registry
+                        "service2", ImmutableMap.of("image", "${WITH_SPECIAL_CHARS}"),
+                        // Test multiple variables in one string
+                        "service3", ImmutableMap.of("image", "${WITH_SPECIAL_CHARS}-${SIMPLE_VAR}"),
+                        // Test undefined variables remain unchanged
+                        "service4", ImmutableMap.of("image", "app:${UNDEFINED_VAR}"),
+                        // Test variables with special characters that don't need substitution
+                        "service5", ImmutableMap.of("image", "app:latest"),
+                        // Test empty variable with default
+                        "service6", ImmutableMap.of("image", "nginx:${EMPTY_VAR:-default}")
+                    )
+                )
+            );
+
+            assertThat(parsedFile.getServiceNameToImageNames())
+                .as("edge cases in variable substitution work correctly")
+                .contains(
+                    entry("service1", Sets.newHashSet("redis:simple-value")),
+                    entry("service2", Sets.newHashSet("registry.io/app:v1.2.3")),
+                    entry("service3", Sets.newHashSet("registry.io/app:v1.2.3-simple-value")),
+                    entry("service4", Sets.newHashSet("app:${UNDEFINED_VAR}")),
+                    entry("service5", Sets.newHashSet("app:latest")),
+                    entry("service6", Sets.newHashSet("nginx:default"))
+                );
+        } finally {
+            // Clean up
+            System.clearProperty("SIMPLE_VAR");
+            System.clearProperty("WITH_SPECIAL_CHARS");
+            System.clearProperty("EMPTY_VAR");
+        }
+    }
 }