JUnit 5 best practices (#343)

---------

Co-authored-by: Moderne <team@moderne.io>
Co-authored-by: Mirko Friedenhagen <mfriedenhagen@gmx.de>

Author: 3 people

pom.xml

@@ -94,16 +94,15 @@
       <artifactId>commons-codec</artifactId>
       <version>1.19.0</version>
     </dependency>
-
-    <!-- testing support -->
     <dependency>
-      <groupId>junit</groupId>
-      <artifactId>junit</artifactId>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <version>4.11.0</version>
       <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.mockito</groupId>
-      <artifactId>mockito-core</artifactId>
+      <artifactId>mockito-junit-jupiter</artifactId>
       <version>4.11.0</version>
       <scope>test</scope>
     </dependency>

src/test/java/org/codehaus/mojo/extraenforcer/dependencies/ClassFileHelper.java

@@ -25,17 +25,16 @@
 import java.nio.file.Files;
 
 import org.apache.maven.artifact.Artifact;
-import org.junit.rules.TemporaryFolder;
 
 /**
  * Test utility to make writing tests with {@link ClassFile}s easier.
  */
 public class ClassFileHelper {
     private static int uniqueId = 0;
 
-    private final TemporaryFolder temporaryFolder;
+    private final File temporaryFolder;
 
-    public ClassFileHelper(TemporaryFolder temporaryFolder) {
+    public ClassFileHelper(File temporaryFolder) {
         this.temporaryFolder = temporaryFolder;
     }
 
@@ -60,7 +59,7 @@ public ClassFile createWithContent(String pathToClassFile, String fileContents)
 
     private File createTempDirectory(String uniqueIdStr) {
         try {
-            return temporaryFolder.newFolder(uniqueIdStr);
+            return newFolder(temporaryFolder, uniqueIdStr);
         } catch (IOException exception) {
             throw new RuntimeException("unable to create temporary folder", exception);
         }
@@ -80,4 +79,13 @@ private void createClassFile(File directory, String pathToClassFile, String file
             writer.write(fileContents);
         }
     }
+
+    private static File newFolder(File root, String... subDirs) throws IOException {
+        String subFolder = String.join("/", subDirs);
+        File result = new File(root, subFolder);
+        if (!result.mkdirs()) {
+            throw new IOException("Couldn't create folders " + root);
+        }
+        return result;
+    }
 }

src/test/java/org/codehaus/mojo/extraenforcer/dependencies/ClassFileTest.java

@@ -1,29 +1,30 @@
 package org.codehaus.mojo.extraenforcer.dependencies;
 
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.TemporaryFolder;
+import java.io.File;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 public class ClassFileTest {
     private static final String PATH_TO_CLASS_FILE =
             ClassFileTest.class.getName().replace('.', '/') + ".class";
 
-    @Rule
-    public TemporaryFolder tempFolder = new TemporaryFolder();
+    @TempDir
+    private File tempFolder;
 
     private final ClassFileHelper classFileHelper = new ClassFileHelper(tempFolder);
 
     @Test
-    public void getHashComputesHashOfFile() throws Exception {
+    void getHashComputesHashOfFile() throws Exception {
         ClassFile classFile = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "the content of the file");
 
         assertEquals("7b7f48e1c0e847133d8881d5743d253756bf44e490e2252556ad4816a0a77b67", classFile.getHash());
     }
 
     @Test
-    public void getHashReturnsConsistentHashWhenInvokedTwice() throws Exception {
+    void getHashReturnsConsistentHashWhenInvokedTwice() throws Exception {
         ClassFile classFile = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "file content");
 
         String hash1 = classFile.getHash();

src/test/java/org/codehaus/mojo/extraenforcer/dependencies/ClassesWithSameNameTest.java

@@ -19,18 +19,19 @@
  * under the License.
  */
 
+import java.io.File;
 import java.util.Set;
 
 import org.apache.maven.artifact.Artifact;
 import org.apache.maven.enforcer.rule.api.EnforcerLogger;
-import org.junit.Before;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.TemporaryFolder;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.Mockito.mock;
 
 public class ClassesWithSameNameTest {
@@ -48,13 +49,13 @@ public class ClassesWithSameNameTest {
 
     private static final EnforcerLogger LOG = mock(EnforcerLogger.class);
 
-    @Rule
-    public TemporaryFolder temporaryFolder = new TemporaryFolder();
+    @TempDir
+    private File temporaryFolder;
 
     private ClassFileHelper classFileHelper;
 
-    @Before
-    public void beforeEachTest() {
+    @BeforeEach
+    void beforeEachTest() {
         classFileHelper = new ClassFileHelper(temporaryFolder);
     }
 
@@ -64,7 +65,7 @@ public void beforeEachTest() {
      * files are exactly the same.
      */
     @Test
-    public void hasDuplicatesShouldReturnTrueWhenClassNameIsDuplicate() throws Exception {
+    void hasDuplicatesShouldReturnTrueWhenClassNameIsDuplicate() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);
@@ -75,7 +76,7 @@ public void hasDuplicatesShouldReturnTrueWhenClassNameIsDuplicate() throws Excep
     }
 
     @Test
-    public void hasDuplicatesShouldReturnFalseWhenClassNameIsDuplicateButBytecodeIsIdentical() throws Exception {
+    void hasDuplicatesShouldReturnFalseWhenClassNameIsDuplicateButBytecodeIsIdentical() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "content matches in both");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "content matches in both");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);
@@ -86,7 +87,7 @@ public void hasDuplicatesShouldReturnFalseWhenClassNameIsDuplicateButBytecodeIsI
     }
 
     @Test
-    public void hasDuplicatesShouldReturnFalseWhenClassHasNoDuplicates() throws Exception {
+    void hasDuplicatesShouldReturnFalseWhenClassHasNoDuplicates() throws Exception {
         ClassFile classFile = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile);
 
@@ -104,7 +105,7 @@ public void hasDuplicatesShouldReturnFalseWhenClassHasNoDuplicates() throws Exce
      * bytecode).
      */
     @Test
-    public void hasDuplicatesShouldReturnTrueWhenClassNameIsDuplicateButBytecodeDiffers() throws Exception {
+    void hasDuplicatesShouldReturnTrueWhenClassNameIsDuplicateButBytecodeDiffers() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "1");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "2");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);
@@ -122,7 +123,7 @@ public void hasDuplicatesShouldReturnTrueWhenClassNameIsDuplicateButBytecodeDiff
      * We set the test up so it finds duplicates only if the bytecode differs.
      */
     @Test
-    public void hasDuplicatesShouldReturnFalseWhenClassNameIsDuplicateAndBytecodeDiffers() throws Exception {
+    void hasDuplicatesShouldReturnFalseWhenClassNameIsDuplicateAndBytecodeDiffers() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "1");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "2");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);
@@ -136,7 +137,7 @@ public void hasDuplicatesShouldReturnFalseWhenClassNameIsDuplicateAndBytecodeDif
      * This tests the normal condition where we just output the class file path.
      */
     @Test
-    public void toOutputStringOutputsPlainArtifactWhenJustNamesAreDuplicate() throws Exception {
+    void toOutputStringOutputsPlainArtifactWhenJustNamesAreDuplicate() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);
@@ -152,7 +153,7 @@ public void toOutputStringOutputsPlainArtifactWhenJustNamesAreDuplicate() throws
      * determine which artifacts they can ignore when fix the BanDuplicateClasses error.
      */
     @Test
-    public void toOutputStringOutputsTwoArtifactsWhereBytecodeIsExactMatch() throws Exception {
+    void toOutputStringOutputsTwoArtifactsWhereBytecodeIsExactMatch() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "content matches in both");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "content matches in both");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);
@@ -171,8 +172,7 @@ public void toOutputStringOutputsTwoArtifactsWhereBytecodeIsExactMatch() throws
      * 1 and 2 don't match 3 and 4.
      */
     @Test
-    public void toOutputStringOutputsFourArtifactsWhereBytecodeIsExactMatchInTwoAndExactMatchInOtherTwo()
-            throws Exception {
+    void toOutputStringOutputsFourArtifactsWhereBytecodeIsExactMatchInTwoAndExactMatchInOtherTwo() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "file content of 1 and 2");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "file content of 1 and 2");
         ClassFile classFile3 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "file content of 3 and 4");
@@ -194,16 +194,15 @@ public void toOutputStringOutputsFourArtifactsWhereBytecodeIsExactMatchInTwoAndE
      * The method should return the 2nd-to-last element in the last, but if there's only 1 element
      * there's no 2nd-to-last element to return.
      */
-    @Test(expected = IllegalArgumentException.class)
-    public void previousShouldThrowIfOnlyOneArtifact() throws Exception {
+    @Test
+    void previousShouldThrowIfOnlyOneArtifact() throws Exception {
         ClassFile classFile = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "file content of 1 and 2");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile);
-
-        classesWithSameName.previous();
+        assertThrows(IllegalArgumentException.class, () -> classesWithSameName.previous());
     }
 
     @Test
-    public void previousShouldReturn2ndToLastElement() throws Exception {
+    void previousShouldReturn2ndToLastElement() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "file content of 1 and 2");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "file content of 1 and 2");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);
@@ -214,7 +213,7 @@ public void previousShouldReturn2ndToLastElement() throws Exception {
     }
 
     @Test
-    public void addShouldAddArtifact() throws Exception {
+    void addShouldAddArtifact() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1);
@@ -224,25 +223,25 @@ public void addShouldAddArtifact() throws Exception {
         assertEquals(2, classesWithSameName.getAllArtifactsThisClassWasFoundIn().size());
     }
 
-    @Test(expected = IllegalArgumentException.class)
-    public void addShouldThrowWhenClassNameDoesNotMatch() throws Exception {
+    @Test
+    void addShouldThrowWhenClassNameDoesNotMatch() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassFile classFile2 = classFileHelper.createWithContent("some/other/path.class", "");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1);
-
-        classesWithSameName.add(classFile2);
+        assertThrows(IllegalArgumentException.class, () -> classesWithSameName.add(classFile2));
     }
 
-    @Test(expected = IllegalArgumentException.class)
-    public void constructorShouldThrowWhenClassNameDoesNotMatch() throws Exception {
+    @Test
+    void constructorShouldThrowWhenClassNameDoesNotMatch() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassFile classFile2 = classFileHelper.createWithContent("some/other/path.class", "");
-
-        new ClassesWithSameName(LOG, classFile1, classFile2);
+        assertThrows(IllegalArgumentException.class, () -> {
+            new ClassesWithSameName(LOG, classFile1, classFile2);
+        });
     }
 
     @Test
-    public void getAllArtifactsThisClassWasFoundInShouldReturnAllArtifacts() throws Exception {
+    void getAllArtifactsThisClassWasFoundInShouldReturnAllArtifacts() throws Exception {
         ClassFile classFile1 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassFile classFile2 = classFileHelper.createWithContent(PATH_TO_CLASS_FILE, "");
         ClassesWithSameName classesWithSameName = new ClassesWithSameName(LOG, classFile1, classFile2);

src/test/java/org/codehaus/mojo/extraenforcer/dependencies/EnforceBytecodeVersionTest.java

@@ -16,14 +16,14 @@
 
 package org.codehaus.mojo.extraenforcer.dependencies;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
-import static org.junit.Assert.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
-public class EnforceBytecodeVersionTest {
+class EnforceBytecodeVersionTest {
 
     @Test
-    public void renderVersion() {
+    void renderVersion() {
         assertEquals("JDK 1.5", EnforceBytecodeVersion.renderVersion(49, 0));
         assertEquals("JDK 1.7", EnforceBytecodeVersion.renderVersion(51, 0));
         assertEquals("JDK 11", EnforceBytecodeVersion.renderVersion(55, 0));

src/test/java/org/codehaus/mojo/extraenforcer/dependencies/JarUtilsTest.java

@@ -1,18 +1,18 @@
 package org.codehaus.mojo.extraenforcer.dependencies;
 
 import org.apache.maven.artifact.Artifact;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import static org.codehaus.mojo.extraenforcer.dependencies.ArtifactBuilder.newBuilder;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
-public class JarUtilsTest {
+class JarUtilsTest {
     /**
      * "Sunny day" test: the method should return true for a jar artifact.
      */
     @Test
-    public void isJarFileShouldReturnTrueForJarFile() {
+    void isJarFileShouldReturnTrueForJarFile() {
         Artifact artifact = newBuilder().withType("jar").build();
         assertTrue(JarUtils.isJarFile(artifact));
     }
@@ -22,7 +22,7 @@ public void isJarFileShouldReturnTrueForJarFile() {
      * a folder with a bunch of packages/class files in it).
      */
     @Test
-    public void isJarFileShouldReturnFalseForDirectory() {
+    void isJarFileShouldReturnFalseForDirectory() {
         Artifact artifact = newBuilder().withType("jar").withAnyDirectory().build();
         assertFalse(JarUtils.isJarFile(artifact));
     }
@@ -32,7 +32,7 @@ public void isJarFileShouldReturnFalseForDirectory() {
      * not "jar". For example: a war or a zip file.
      */
     @Test
-    public void isJarFileShouldReturnFalseWhenArtifactTypeIsNotJar() {
+    void isJarFileShouldReturnFalseWhenArtifactTypeIsNotJar() {
         Artifact artifact = newBuilder().withType("war").build();
         assertFalse(JarUtils.isJarFile(artifact));
     }

src/test/java/org/codehaus/mojo/extraenforcer/encoding/RequireEncodingTest.java

@@ -6,28 +6,28 @@
 import org.apache.maven.enforcer.rule.api.EnforcerLogger;
 import org.apache.maven.enforcer.rule.api.EnforcerRuleException;
 import org.apache.maven.project.MavenProject;
-import org.junit.Before;
-import org.junit.Test;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
 
-import static org.junit.Assert.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
-public class RequireEncodingTest {
+class RequireEncodingTest {
 
     private RequireEncoding rule;
 
     private MavenProject project;
 
-    @Before
-    public void initFields() {
+    @BeforeEach
+    void initFields() {
         project = mock(MavenProject.class);
         rule = new RequireEncoding(project);
         rule.setLog(mock(EnforcerLogger.class));
     }
 
     @Test
-    public void failUTF8() throws Exception {
+    void failUTF8() throws Exception {
 
         when(project.getBasedir()).thenReturn(new File("src/test/resources").getAbsoluteFile());