testing_faq: initial

ijs.tree

@@ -215,6 +215,7 @@
         <toc-element id="test_project_and_testdata_directories.md"/>
         <toc-element id="writing_tests.md"/>
         <toc-element id="testing_highlighting.md"/>
+        <toc-element id="testing_faq.md"/>
     </toc-element>
     <toc-element toc-title="Part VII - Custom Languages">
         <toc-element id="custom_language_support.md">

topics/basics/testing_plugins/testing_faq.md

@@ -0,0 +1,67 @@
+[//]: # (title: Testing FAQ)
+
+<!-- Copyright 2000-2021 JetBrains s.r.o. and other contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file. -->
+
+This page lists a number of common questions/issues and techniques useful for testing plugins.
+
+## Useful Classes
+
+- [`UsefulTestCase`](upsource:///platform/testFramework/src/com/intellij/testFramework/UsefulTestCase.java)
+- [`PlatformTestUtil`](upsource:///platform/testFramework/src/com/intellij/testFramework/PlatformTestUtil.java)
+- [`CodeInsightTestUtil`](upsource:///platform/testFramework/src/com/intellij/testFramework/fixtures/CodeInsightTestUtil.java)
+- [`EditorTestUtil`](upsource:///platform/testFramework/src/com/intellij/testFramework/EditorTestUtil.java)
+- [`PsiTestUtil`](upsource:///platform/testFramework/src/com/intellij/testFramework/PsiTestUtil.java)
+- [`VfsTestUtil`](upsource:///platform/testFramework/src/com/intellij/testFramework/VfsTestUtil.java)
+- [`ProjectViewTestUtil`](upsource:///platform/testFramework/src/com/intellij/testFramework/ProjectViewTestUtil.java)
+- [`TestLookupElementPresentation`](upsource:///platform/testFramework/src/com/intellij/testFramework/fixtures/TestLookupElementPresentation.java)
+
+## Issues
+
+### How to avoid blinking tests?
+
+- Always call `super.tearDown()` inside `finally {..}` block of your test class to avoid leaks and side-effects from previously run (failed) tests.
+- Avoid OS-specific assumptions (e.g., filesystem case-sensitivity, use `java.io.File.separator`).
+- Use _ordered_ collections if necessary or use [`UsefulTestCase#assertUnorderedCollection()`](upsource:///platform/testFramework/src/com/intellij/testFramework/UsefulTestCase.java).
+- Code deferring execution (e.g., via `Application#invokeLater()`) might not run during test execution (and possibly fails in production, too). Use `invokeLater(runnable, myProject.getDisposed()`.
+
+### How to avoid test failure when using resources?
+
+In some situations, added or changed files (e.g. DTDs provided by plugin) are not refreshed in VFS. In such cases, simply delete <path>test-system/caches</path> in your [sandbox directory](ide_development_instance.md#the-development-instance-sandbox-directory) and try again.
+
+## Techniques
+                         
+### How to mark test-only elements in production code?
+
+Annotate with [`org.jetbrains.annotations.TestOnly`](https://github.com/JetBrains/java-annotations/blob/master/common/src/main/java/org/jetbrains/annotations/TestOnly.java), usages will be highlighted via inspection <control>JVM languages | Test-only usage in production code</control>.
+
+### How to run tests for all files in a directory?
+
+Use [`FileBasedTestCaseHelper`](upsource:///platform/testFramework/src/com/intellij/testFramework/FileBasedTestCaseHelper.java), please see its javadoc for instructions.
+
+### How to modify setup on per-test basis?
+
+Use `UsefulTestCase.getTestName()` or create your own annotation(s) which can be checked via `UsefulTestCase.annotatedWith()`.
+
+### How to dispatch pending UI events?
+
+Use [`PlatformTestUtil.dispatchAllInvocationEventsInIdeEventQueue()`](upsource:///platform/testFramework/src/com/intellij/testFramework/PlatformTestUtil.java).
+
+### How to disable stderr logging?
+
+Use [`DefaultLogger.disableStderrDumping()`](upsource:///platform/util/src/com/intellij/openapi/diagnostic/DefaultLogger.java) passing `getTestRootDisposable()`.
+
+### How to register a resource (DTD, XSD) temporarily?
+
+Use `com.intellij.javaee.ExternalResourceManagerExImpl.registerResourceTemporarily()` passing `getTestRootDisposable()`. 
+                     
+### How to replace component/service in tests?
+
+Provide `testServiceImplementation` for service declaration in <path>plugin.xml</path>, or use [`ServiceContainerUtil`](upsource:///platform/testFramework/src/com/intellij/testFramework/ServiceContainerUtil.kt).
+                  
+### How to wait for specified amount of time?
+
+Use `com.intellij.util.TimeoutUtil.sleep()`.
+
+### JVM: How to add Maven dependencies?
+
+Use [`MavenDependencyUtil`](upsource:///java/testFramework/src/com/intellij/testFramework/fixtures/MavenDependencyUtil.java).

topics/basics/testing_plugins/testing_plugins.md

@@ -35,6 +35,7 @@ Please do not use _platform/testGuiFramework_; it is reserved for internal use.
 * [Test Project and Testdata Directories](test_project_and_testdata_directories.md)
 * [Writing Tests](writing_tests.md)
 * [Testing Highlighting](testing_highlighting.md)
+* [Testing FAQ](testing_faq.md)
 
   > Check out [this step-by-step tutorial](writing_tests_for_plugins.md) teaching how to write and run automated tests for your custom language plugin (source code included).
   >