JMockit to Mockito Migration Recipe - Rewrite Expectations Block (#415)

* Recipe to convert JMockit Expectations block to Mockito.when statement

---------

Co-authored-by: Kun Li <kun@moderne.io>

build.gradle.kts

@@ -19,6 +19,7 @@ recipeDependencies {
     parserClasspath("com.github.tomakehurst:wiremock-jre8:2.35.0")
     parserClasspath("org.mockito:mockito-all:1.10.19")
     parserClasspath("org.mockito:mockito-core:3.+")
+    parserClasspath("org.jmockit:jmockit:1.49")
     parserClasspath("org.mockito:mockito-junit-jupiter:3.+")
     parserClasspath("org.powermock:powermock-api-mockito:1.7.+")
     parserClasspath("org.powermock:powermock-core:1.7.+")

src/main/java/org/openrewrite/java/testing/jmockit/JMockitExpectationsToMockitoWhen.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2023 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.testing.jmockit;
+
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Preconditions;
+import org.openrewrite.Recipe;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.JavaParser;
+import org.openrewrite.java.JavaTemplate;
+import org.openrewrite.java.JavaVisitor;
+import org.openrewrite.java.search.UsesType;
+import org.openrewrite.java.tree.Expression;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.Statement;
+
+@Value
+@EqualsAndHashCode(callSuper = false)
+public class JMockitExpectationsToMockitoWhen extends Recipe {
+  @Override
+  public String getDisplayName() {
+    return "Rewrite JMockit Expectations";
+  }
+
+  @Override
+  public String getDescription() {
+    return "Rewrites JMockit `Expectations` to `Mockito.when`.";
+  }
+
+  @Override
+  public TreeVisitor<?, ExecutionContext> getVisitor() {
+    return Preconditions.check(new UsesType<>("mockit.*", false),
+        new RewriteExpectationsVisitor());
+  }
+
+  private static class RewriteExpectationsVisitor extends JavaVisitor<ExecutionContext> {
+    @Override
+    public J visitNewClass(J.NewClass newClass, ExecutionContext executionContext) {
+      J.NewClass nc = (J.NewClass) super.visitNewClass(newClass, executionContext);
+      if (!(nc.getClazz() instanceof J.Identifier)) {
+        return nc;
+      }
+      J.Identifier clazz = (J.Identifier) nc.getClazz();
+      if (!clazz.getSimpleName().equals("Expectations")) {
+        return nc;
+      }
+
+      // empty Expectations block is considered invalid
+      assert nc.getBody() != null : "Expectations block is empty";
+
+      // prepare the statements for moving
+      J.Block innerBlock = (J.Block) nc.getBody().getStatements().get(0);
+
+      // TODO: handle multiple mock statements
+      Statement mockInvocation = innerBlock.getStatements().get(0);
+      Expression result = ((J.Assignment) innerBlock.getStatements().get(1)).getAssignment();
+
+      // apply the template and replace the `new Expectations()` statement coordinates
+      // TODO: handle exception results with another template
+      J.MethodInvocation newMethod = JavaTemplate.builder("when(#{any()}).thenReturn(#{});")
+          .javaParser(JavaParser.fromJavaVersion().classpathFromResources(executionContext, "mockito-core-3.12"))
+          .staticImports("org.mockito.Mockito.when")
+          .build()
+          .apply(
+              getCursor(),
+              nc.getCoordinates().replace(),
+              mockInvocation,
+              result
+          );
+
+      // handle import changes
+      maybeAddImport("org.mockito.Mockito", "when");
+      maybeRemoveImport("mockit.Expectations");
+
+      return newMethod.withPrefix(nc.getPrefix());
+    }
+  }
+}

src/main/resources/META-INF/rewrite/jmockit.yml

@@ -0,0 +1,31 @@
+#
+# Copyright 2023 the original author or authors.
+# <p>
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+# <p>
+# https://www.apache.org/licenses/LICENSE-2.0
+# <p>
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+---
+type: specs.openrewrite.org/v1beta/recipe
+name: org.openrewrite.java.testing.jmockit.JMockitToMockito
+displayName: Migrate from JMockit to Mockito
+description: This recipe will apply changes commonly needed when migrating from JMockit to Mockito.
+tags:
+  - testing
+  - jmockit
+recipeList:
+  - org.openrewrite.java.ChangeType:
+      oldFullyQualifiedTypeName: mockit.Mocked
+      newFullyQualifiedTypeName: org.mockito.Mock
+  - org.openrewrite.java.ChangeType:
+      oldFullyQualifiedTypeName: mockit.integration.junit5.JMockitExtension
+      newFullyQualifiedTypeName: org.mockito.junit.jupiter.MockitoExtension
+  - org.openrewrite.java.testing.jmockit.JMockitExpectationsToMockitoWhen

src/test/java/org/openrewrite/java/testing/jmockit/JMockitToMockitoTest.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright 2023 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.testing.jmockit;
+
+import static org.openrewrite.java.Assertions.java;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.InMemoryExecutionContext;
+import org.openrewrite.java.JavaParser;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+class JMockitToMockitoTest implements RewriteTest {
+
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec
+          .parser(JavaParser.fromJavaVersion()
+            .logCompilationWarningsAndErrors(true)
+            .classpathFromResources(new InMemoryExecutionContext(),
+              "junit-jupiter-api-5.9",
+              "jmockit-1.49",
+              "mockito-core-3.12",
+              "mockito-junit-jupiter-3.12"
+            ))
+          .recipeFromResource(
+            "/META-INF/rewrite/jmockit.yml",
+            "org.openrewrite.java.testing.jmockit.JMockitToMockito"
+          );
+    }
+
+    @Test
+    void jMockitExpectationsToMockitoWhen() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class MyObject {
+                  public String getSomeField() {
+                      return "X";
+                  }
+              }
+              """
+          ),
+          java(
+            """
+              import static org.junit.jupiter.api.Assertions.assertNull;
+
+              import mockit.Expectations;
+              import mockit.Mocked;
+              import mockit.integration.junit5.JMockitExtension;
+              import org.junit.jupiter.api.extension.ExtendWith;
+
+              @ExtendWith(JMockitExtension.class)
+              class MyTest {
+                @Mocked
+                MyObject myObject;
+
+                void test() {
+                  new Expectations() {{
+                    myObject.getSomeField();
+                    result = null;
+                  }};
+                  assertNull(myObject.getSomeField());
+                }
+              }
+              """,
+            """
+              import static org.junit.jupiter.api.Assertions.assertNull;
+              import static org.mockito.Mockito.when;
+
+              import org.junit.jupiter.api.extension.ExtendWith;
+              import org.mockito.Mock;
+              import org.mockito.junit.jupiter.MockitoExtension;
+
+              @ExtendWith(MockitoExtension.class)
+              class MyTest {
+                @Mock
+                MyObject myObject;
+
+                void test() {
+                  when(myObject.getSomeField()).thenReturn(null);
+                  assertNull(myObject.getSomeField());
+                }
+              }
+              """
+          )
+        );
+    }
+}