[Gradle] Add a warning mode assertion for the old test DSL tests

#KT-55972 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/BaseGradleIT.kt

@@ -425,7 +425,9 @@ abstract class BaseGradleIT {
         var result: ProcessRunResult? = null
         try {
             result = runProcess(cmd, projectDir, env, buildOptions)
-            CompiledProject(this, result.output, result.exitCode).check()
+            val compiledProject = CompiledProject(this, result.output, result.exitCode)
+            compiledProject.check()
+            compiledProject.additionalAssertions(buildOptions)
         } catch (t: Throwable) {
             println("<=== Test build: $projectName $cmd ===>")
 
@@ -441,6 +443,23 @@ abstract class BaseGradleIT {
         }
     }
 
+    private fun CompiledProject.additionalAssertions(options: BuildOptions) {
+        if (options.warningMode != WarningMode.Fail) {
+            assertDeprecationWarningsArePresent(options.warningMode)
+        }
+    }
+
+    private fun CompiledProject.assertDeprecationWarningsArePresent(warningMode: WarningMode) {
+        assertContains(
+            "[GradleWarningsDetectorPlugin] The plugin is being applied",
+            errorMessage = NO_GRADLE_WARNINGS_DETECTOR_PLUGIN_ERROR_MESSAGE
+        )
+        assertContains(
+            "[GradleWarningsDetectorPlugin] Some deprecation warnings were found during this build.",
+            errorMessage = getWarningModeChangeAdvice(warningMode)
+        )
+    }
+
     fun <T> Project.getModels(modelType: Class<T>): ModelContainer<T> {
         if (!projectDir.exists()) {
             setupWorkingDir()
@@ -484,9 +503,9 @@ abstract class BaseGradleIT {
         return this
     }
 
-    fun CompiledProject.assertContains(vararg expected: String, ignoreCase: Boolean = false): CompiledProject {
+    fun CompiledProject.assertContains(vararg expected: String, ignoreCase: Boolean = false, errorMessage: String? = null): CompiledProject {
         for (str in expected) {
-            assertTrue(output.contains(str.normalize(), ignoreCase), "Output should contain '$str'")
+            assertTrue(output.contains(str.normalize(), ignoreCase), errorMessage ?: "Output should contain '$str'")
         }
         return this
     }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/testbase/outputAssertions.kt

@@ -193,22 +193,25 @@ fun BuildResult.assertBuildReportPathIsPrinted() {
     assertOutputContains("Kotlin build report is written to file://")
 }
 
+val NO_GRADLE_WARNINGS_DETECTOR_PLUGIN_ERROR_MESSAGE =
+    """
+    The build uses warning mode other than `${WarningMode.Fail}` and uses a non-default project settings file.
+    Please apply the `org.jetbrains.kotlin.test.gradle-warnings-detector` plugin to the settings.
+
+    """.trimIndent()
+
+fun getWarningModeChangeAdvice(warningMode: WarningMode) =
+    "Warning mode is set to `$warningMode`, but the build produced no deprecation warnings. Please set it to `${WarningMode.Fail}`"
+
 /**
  * Asserts that the build produced some deprecation warnings.
  *
  * Expected to be executed only for the case when [BuildOptions.warningMode] is not set to [WarningMode.Fail]
  */
 fun BuildResult.assertDeprecationWarningsArePresent(warningMode: WarningMode) {
-    assertOutputContains(
+    assertOutputContains("[GradleWarningsDetectorPlugin] The plugin is being applied", NO_GRADLE_WARNINGS_DETECTOR_PLUGIN_ERROR_MESSAGE)
-        "[GradleWarningsDetectorPlugin] The plugin is being applied",
-        """
-            The build uses warning mode other than `${WarningMode.Fail}` and uses a non-default project settings file.
-            Please apply the `org.jetbrains.kotlin.test.gradle-warnings-detector` plugin to the settings.
-
-        """.trimIndent()
-    )
     assertOutputContains(
         "[GradleWarningsDetectorPlugin] Some deprecation warnings were found during this build.",
-        "Warning mode is set to `$warningMode`, but the build produced no deprecation warnings. Please set it to `${WarningMode.Fail}`"
+        getWarningModeChangeAdvice(warningMode)
     )
 }