[Gradle, JS] Ignore stdout for mocha dry run

^KT-61992 fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/Kotlin2JsGradlePluginIT.kt

@@ -1298,6 +1298,17 @@ class Kotlin2JsIrGradlePluginIT : KGPBaseTest() {
             )
             buildAndFail("nodeTest") {
                 assertTasksFailed(":nodeTest")
+                assertOutputContains("Cannot find module 'foo'")
+            }
+        }
+    }
+
+    @DisplayName("mocha has no output during dry run")
+    @GradleTest
+    fun testMochaHasNoDryRunOutput(gradleVersion: GradleVersion) {
+        project("kotlin-js-nodejs-project", gradleVersion) {
+            build("nodeTest") {
+                assertOutputDoesNotContain("0 passing")
             }
         }
     }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/internal/testing/TCServiceMessagesTestExecutor.kt

@@ -59,6 +59,12 @@ class TCServiceMessagesTestExecutor(
             if (spec.dryRunArgs != null) {
                 val exec = execHandleFactory.newExec()
                 spec.forkOptions.copyTo(exec)
+                // get rid of redundant output during dry-run
+                exec.standardOutput = object : OutputStream() {
+                    override fun write(b: Int) {
+                         // do nothing
+                    }
+                }
                 exec.args = spec.dryRunArgs
                 execHandle = exec.build()