navigate to testdata: add tests for multifile test data

plugins/devkit/devkit-java-tests/testData/guessByExistingFiles/SomeTestWithTestDataDir.java

@@ -0,0 +1,6 @@
+import junit.framework.TestCase;
+
+public class SomeTestWithTestDataDir extends TestCase {
+  public void test<caret>TestDataForThisTest() {
+  }
+}

plugins/devkit/devkit-java-tests/testData/guessByExistingFiles/SomeTestWithTestDataDirAndSibling.java

@@ -0,0 +1,10 @@
+import junit.framework.TestCase;
+
+public class SomeTestWithTestDataDir extends TestCase {
+  public void testIntelliJ<caret>IDEA() {
+
+  }
+
+  public void testTestDataForThisTest() {
+  }
+}

plugins/devkit/devkit-java-tests/testSrc/org/jetbrains/idea/devkit/testAssistant/TestDataGuessByExistingFilesUtilTest.java

@@ -18,6 +18,7 @@ package org.jetbrains.idea.devkit.testAssistant;
 import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.projectRoots.ex.JavaSdkUtil;
 import com.intellij.openapi.util.ThrowableComputable;
+import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.psi.PsiClass;
 import com.intellij.psi.PsiMethod;
@@ -25,6 +26,7 @@ import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.testFramework.PsiTestUtil;
 import com.intellij.testFramework.TestDataPath;
 import com.intellij.testFramework.builders.JavaModuleFixtureBuilder;
+import com.intellij.util.PathUtil;
 import com.intellij.util.containers.ContainerUtil;
 import org.jetbrains.idea.devkit.DevkitJavaTestsUtil;
 import org.jetbrains.jps.model.java.JavaResourceRootType;
@@ -127,6 +129,29 @@ public class TestDataGuessByExistingFilesUtilTest extends TestDataPathTestCase {
     verifyResultForOnlySame(result);
   }
 
+  public void testCollectTestDataByDirName() {
+    PsiMethod testMethod = getTestMethodWithTestDataDir();
+    List<TestDataFile> result = TestDataGuessByExistingFilesUtil.suggestTestDataFiles(
+      TestDataGuessByExistingFilesUtil.getTestName(testMethod.getName()), null, testMethod.getContainingClass());
+    assertSize(2, result);
+    assertTrue(result.get(0).exists() && result.get(1).exists());
+    assertEquals(ContainerUtil.set("before.java", "after.java"), ContainerUtil.map2Set(result, TestDataFile::getName));
+  }
+
+  public void testGuessTestDataByRelatedByDirName() {
+    PsiMethod testMethod = getTestMethodWithTestDataDirAndSibling();
+
+    List<TestDataFile> result = TestDataGuessByExistingFilesUtil.guessTestDataName(testMethod);
+    assertSize(2, result);
+    assertTrue(!result.get(0).exists() && !result.get(1).exists());
+    assertEquals(ContainerUtil.set("before.java", "after.java"), ContainerUtil.map2Set(result, TestDataFile::getName));
+    String parentName1 = PathUtil.getFileName(PathUtil.getParentPath(result.get(0).getPath()));
+    String parentName2 = PathUtil.getFileName(PathUtil.getParentPath(result.get(1).getPath()));
+
+    String expected = StringUtil.decapitalize(TestDataGuessByExistingFilesUtil.getTestName(testMethod.getName()));
+    assertEquals(expected, parentName1);
+    assertEquals(expected, parentName2);
+  }
 
   private PsiMethod getTestMethodWithBeforeAndAfterTestData() {
     return getTestMethod("SomeTest_BeforeAndAfter.java", "somethingBA_before.java", "somethingBA_after.java");
@@ -140,6 +165,14 @@ public class TestDataGuessByExistingFilesUtilTest extends TestDataPathTestCase {
     return getTestMethod("SomeTest_AfterAndSame.java", "somethingAS_after.java", "somethingAS.java");
   }
 
+  private PsiMethod getTestMethodWithTestDataDir() {
+    return getTestMethod("SomeTestWithTestDataDir.java", "testDataForThisTest/before.java", "testDataForThisTest/after.java");
+  }
+
+  private PsiMethod getTestMethodWithTestDataDirAndSibling() {
+    return getTestMethod("SomeTestWithTestDataDirAndSibling.java", "testDataForThisTest/before.java", "testDataForThisTest/after.java");
+  }
+
   private PsiMethod getTestMethodWithOnlySameTestData() {
     return getTestMethod("SomeTest_OnlySame.java", "somethingS.java");
   }