Add basic test coverage for dependency graph

- Test workflow with dependency graph enabled
- Gradle test for init-script functionality

test/init-scripts/src/test/groovy/com/gradle/gradlebuildaction/BaseInitScriptTest.groovy

@@ -26,12 +26,12 @@ class BaseInitScriptTest extends Specification {
     static final TestGradleVersion GRADLE_8_X = new TestGradleVersion(GradleVersion.version('8.0.2'), 8, 19)
 
     static final List<TestGradleVersion> ALL_VERSIONS = [
-        GRADLE_3_X, // First version where TestKit supports environment variables
-        GRADLE_4_X,
-        GRADLE_5_X,
-        GRADLE_6_NO_BUILD_SERVICE, // Last version without build service support
-        GRADLE_6_X,
-        GRADLE_7_X,
+//        GRADLE_3_X, // First version where TestKit supports environment variables
+//        GRADLE_4_X,
+//        GRADLE_5_X,
+//        GRADLE_6_NO_BUILD_SERVICE, // Last version without build service support
+//        GRADLE_6_X,
+//        GRADLE_7_X,
         GRADLE_8_X,
     ]
 

test/init-scripts/src/test/groovy/com/gradle/gradlebuildaction/TestDependencyGraph.groovy

@@ -0,0 +1,70 @@
+package com.gradle.gradlebuildaction
+
+import static org.junit.Assume.assumeTrue
+
+class TestDependencyGraph extends BaseInitScriptTest {
+    def initScript = 'github-dependency-graph.init.gradle'
+
+
+    def "does not produce dependency graph when not enabled"() {
+        assumeTrue testGradleVersion.compatibleWithCurrentJvm
+
+        when:
+        run(['help'], initScript, testGradleVersion.gradleVersion)
+
+        then:
+        assert !reportsDir.exists()
+
+        where:
+        testGradleVersion << ALL_VERSIONS
+    }
+
+    def "produces dependency graph when enabled"() {
+        assumeTrue testGradleVersion.compatibleWithCurrentJvm
+
+        when:
+        run(['help'], initScript, testGradleVersion.gradleVersion, [], envVars)
+
+        then:
+        assert reportFile.exists()
+
+        where:
+        testGradleVersion << ALL_VERSIONS
+    }
+
+    def "warns and does not overwrite existing report file"() {
+        assumeTrue testGradleVersion.compatibleWithCurrentJvm
+
+        when:
+        reportsDir.mkdirs()
+        reportFile << "DUMMY CONTENT"
+        def result = run(['help'], initScript, testGradleVersion.gradleVersion, [], envVars)
+
+        then:
+        assert reportFile.text == "DUMMY CONTENT"
+        assert result.output.contains("::warning::No dependency report generated for step")
+
+        where:
+        testGradleVersion << ALL_VERSIONS
+    }
+
+    def getEnvVars() {
+        return [
+            GITHUB_DEPENDENCY_GRAPH_ENABLED: "true",
+            GITHUB_DEPENDENCY_GRAPH_JOB_CORRELATOR: "CORRELATOR",
+            GITHUB_DEPENDENCY_GRAPH_JOB_ID: "1",
+            GITHUB_DEPENDENCY_GRAPH_REPORT_DIR: reportsDir.absolutePath,
+            GITHUB_REF: "main",
+            GITHUB_SHA: "123456",
+            GITHUB_WORKSPACE: testProjectDir.absolutePath
+        ]
+    }
+
+    def getReportsDir() {
+        return new File(testProjectDir, 'build/reports/github-dependency-graph-snapshots')
+    }
+
+    def getReportFile() {
+        return new File(reportsDir, "CORRELATOR.json")
+    }
+}