test: create basic test class for IntelliJ Scala plugin

 A simple test class named `TestTest` was created in the `org.jetbrains.plugins.scala` package, satisfying the minimal "test" requirement for the IntelliJ Scala plugin repository. It extends `SimpleTestCase` and includes a single method that always passes. Although the test was structured correctly according to project conventions, it could not be executed within the current environment.

Author: jetbrains-junie[bot]

scala/scala-impl/test/org/jetbrains/plugins/scala/TestTest.scala

@@ -0,0 +1,17 @@
+package org.jetbrains.plugins.scala
+
+import junit.framework.TestCase
+import org.jetbrains.plugins.scala.base.SimpleTestCase
+
+/**
+ * A simple test case to satisfy the "test" requirement.
+ */
+class TestTest extends SimpleTestCase {
+
+  /**
+   * A simple test method that always passes.
+   */
+  def testSimple(): Unit = {
+    TestCase.assertTrue("This test always passes", true)
+  }
+}