chore: Migrate Gapic-Generator-Java to JUnit5 (#2771)

Fixes: #2725

# Scope
This *only* modifies the unit tests inside the gapic-generator-java
module. It does not modify the generated unit tests output from the
generator. JUnit4 is still needed with default scope as it's used to
generate the unit tests from the TestComposer:
https://github.com/googleapis/sdk-platform-java/blob/96e6626eb2dda867b5d8d81f3ec706b5a995a3c2/gapic-generator-java/pom.xml#L446-L450

# Changes
- Change the scope for Unit Tests from public to package-private
- Parameterized tests updated to use `@ParameterizedTests`
- Import updated to `org.junit.jupiter.api.*`

gapic-generator-java/pom.xml

@@ -476,5 +476,17 @@
       <version>4.12</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-engine</artifactId>
+      <version>${junit.version}</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-params</artifactId>
+      <version>${junit.version}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

gapic-generator-java/src/test/java/com/google/api/generator/engine/JavaCodeGeneratorTest.java

@@ -60,9 +60,9 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Stack;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
-public class JavaCodeGeneratorTest {
+class JavaCodeGeneratorTest {
 
   private static final String GOLDENFILES_DIRECTORY =
       "src/test/java/com/google/api/generator/engine/goldens/";
@@ -101,7 +101,7 @@ public class JavaCodeGeneratorTest {
   private static final Variable bookKindVar = createVarFromVaporRef(bookKindRef, "bookKind");
 
   @Test
-  public void validJavaClass() {
+  void validJavaClass() {
     // Create outer class variableDecls.
     // [code] private static final String serviceName = "LibraryServiceStub";
     VariableExpr serviceName = createServiceNameVarExpr();

gapic-generator-java/src/test/java/com/google/api/generator/engine/ast/AnonymousClassExprTest.java

@@ -20,11 +20,11 @@
 
 import com.google.common.base.Function;
 import java.util.Arrays;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
-public class AnonymousClassExprTest {
+class AnonymousClassExprTest {
   @Test
-  public void validAnonymousClass_basic() {
+  void validAnonymousClass_basic() {
     ConcreteReference ref = ConcreteReference.withClazz(Runnable.class);
     TypeNode type = TypeNode.withReference(ref);
     AssignmentExpr assignmentExpr = createAssignmentExpr("foobar", "false", TypeNode.BOOLEAN);
@@ -45,7 +45,7 @@ public void validAnonymousClass_basic() {
   }
 
   @Test
-  public void validAnonymousClass_genericAndVariableExpr() {
+  void validAnonymousClass_genericAndVariableExpr() {
     // [Constructing] new Function<String, String>()
     ConcreteReference ref =
         ConcreteReference.builder()
@@ -100,14 +100,14 @@ public void validAnonymousClass_genericAndVariableExpr() {
   }
 
   @Test
-  public void invalidAnonymousClass_primitiveType() {
+  void invalidAnonymousClass_primitiveType() {
     assertThrows(
         IllegalStateException.class,
         () -> AnonymousClassExpr.builder().setType(TypeNode.INT).build());
   }
 
   @Test
-  public void invalidAnonymousClass_staticMethod() {
+  void invalidAnonymousClass_staticMethod() {
     ConcreteReference ref = ConcreteReference.withClazz(Runnable.class);
     TypeNode type = TypeNode.withReference(ref);
     MethodDefinition method =
@@ -127,7 +127,7 @@ public void invalidAnonymousClass_staticMethod() {
   }
 
   @Test
-  public void invalidAnonymousClass_explicitConstructor() {
+  void invalidAnonymousClass_explicitConstructor() {
     TypeNode type = TypeNode.withReference(ConcreteReference.withClazz(Runnable.class));
     TypeNode returnType =
         TypeNode.withReference(
@@ -143,7 +143,7 @@ public void invalidAnonymousClass_explicitConstructor() {
   }
 
   @Test
-  public void invalidAnonymousClass_staticVariableExpr() {
+  void invalidAnonymousClass_staticVariableExpr() {
     ConcreteReference ref = ConcreteReference.withClazz(Runnable.class);
     TypeNode type = TypeNode.withReference(ref);
     Variable variable = createVariable("s", TypeNode.STRING);

gapic-generator-java/src/test/java/com/google/api/generator/engine/ast/ArithmeticOperationExprTest.java

@@ -16,11 +16,11 @@
 
 import static org.junit.Assert.assertThrows;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
-public class ArithmeticOperationExprTest {
+class ArithmeticOperationExprTest {
   @Test
-  public void concatOperator_validBasic() {
+  void concatOperator_validBasic() {
     // valid type-checking for x + getSomeString()
     VariableExpr lhsExpr =
         VariableExpr.withVariable(Variable.builder().setType(TypeNode.INT).setName("x").build());
@@ -34,7 +34,7 @@ public void concatOperator_validBasic() {
   }
 
   @Test
-  public void concatOperator_validWithNull() {
+  void concatOperator_validWithNull() {
     // Type-checking for String variable x and null object value.
     VariableExpr lhsExpr =
         VariableExpr.withVariable(Variable.builder().setType(TypeNode.STRING).setName("x").build());
@@ -44,7 +44,7 @@ public void concatOperator_validWithNull() {
   }
 
   @Test
-  public void concatOperator_validWithReferenceType() {
+  void concatOperator_validWithReferenceType() {
     // Type-checking for String variable x, Expr variable y.
     VariableExpr lhsExpr =
         VariableExpr.withVariable(Variable.builder().setType(TypeNode.STRING).setName("x").build());
@@ -59,7 +59,7 @@ public void concatOperator_validWithReferenceType() {
   }
 
   @Test
-  public void concatOperator_invalidVoidType() {
+  void concatOperator_invalidVoidType() {
     // throw exception if one of expr is void-type
     VariableExpr lhsExpr =
         VariableExpr.withVariable(Variable.builder().setType(TypeNode.STRING).setName("x").build());
@@ -74,7 +74,7 @@ public void concatOperator_invalidVoidType() {
   }
 
   @Test
-  public void concatString_invalidNonStringType() {
+  void concatString_invalidNonStringType() {
     // throw exception for concat usage if none of exprs is String-type
     VariableExpr lhsExpr =
         VariableExpr.withVariable(Variable.builder().setType(TypeNode.INT).setName("x").build());

gapic-generator-java/src/test/java/com/google/api/generator/engine/ast/ArrayExprTest.java

@@ -18,12 +18,12 @@
 import static org.junit.Assert.assertThrows;
 
 import com.google.api.generator.test.utils.TestExprBuilder;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
-public class ArrayExprTest {
+class ArrayExprTest {
 
   @Test
-  public void validAnonymousArray_sametype() {
+  void validAnonymousArray_sametype() {
     ArrayExpr.Builder exprBuilder =
         ArrayExpr.builder()
             .setType(TypeNode.createArrayTypeOf(TypeNode.STRING))
@@ -41,15 +41,15 @@ public void validAnonymousArray_sametype() {
   }
 
   @Test
-  public void validAnonymousArray_unsetTypeThrows() {
+  void validAnonymousArray_unsetTypeThrows() {
     ArrayExpr.Builder exprBuilder = ArrayExpr.builder();
     IllegalStateException thrown =
         assertThrows(IllegalStateException.class, () -> exprBuilder.build());
     assertThat(thrown).hasMessageThat().contains("Property \"type\" has not been set");
   }
 
   @Test
-  public void validAnonymousArray_onlyVariableAndValueExprs() {
+  void validAnonymousArray_onlyVariableAndValueExprs() {
     ArrayExpr.Builder exprBuilder =
         ArrayExpr.builder().setType(TypeNode.createArrayTypeOf(TypeNode.INT));
     Variable variable = Variable.builder().setName("x").setType(TypeNode.INT).build();

gapic-generator-java/src/test/java/com/google/api/generator/engine/ast/AssignmentExprTest.java

@@ -19,11 +19,11 @@
 
 import java.util.ArrayList;
 import java.util.List;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
-public class AssignmentExprTest {
+class AssignmentExprTest {
   @Test
-  public void assignMatchingValue() {
+  void assignMatchingValue() {
     Variable variable = Variable.builder().setName("x").setType(TypeNode.INT).build();
     VariableExpr variableExpr =
         VariableExpr.builder().setVariable(variable).setIsDecl(true).build();
@@ -35,7 +35,7 @@ public void assignMatchingValue() {
   }
 
   @Test
-  public void assignMismatchedValue() {
+  void assignMismatchedValue() {
     Variable variable = Variable.builder().setName("x").setType(TypeNode.BOOLEAN).build();
     VariableExpr variableExpr =
         VariableExpr.builder().setVariable(variable).setIsDecl(true).build();
@@ -47,7 +47,7 @@ public void assignMismatchedValue() {
   }
 
   @Test
-  public void assignSubtypeValue() {
+  void assignSubtypeValue() {
     Variable variable =
         Variable.builder()
             .setName("x")
@@ -66,7 +66,7 @@ public void assignSubtypeValue() {
   }
 
   @Test
-  public void assignMatchingVariable() {
+  void assignMatchingVariable() {
     Variable variable = Variable.builder().setName("x").setType(TypeNode.INT).build();
     VariableExpr variableExpr =
         VariableExpr.builder().setVariable(variable).setIsDecl(true).build();
@@ -78,7 +78,7 @@ public void assignMatchingVariable() {
   }
 
   @Test
-  public void assignNullObjectValue() {
+  void assignNullObjectValue() {
     Variable variable = Variable.builder().setName("x").setType(TypeNode.STRING).build();
     VariableExpr variableExpr =
         VariableExpr.builder().setVariable(variable).setIsDecl(true).build();
@@ -90,7 +90,7 @@ public void assignNullObjectValue() {
   }
 
   @Test
-  public void writeAssignmentExpr_nullObjectValuePrimitiveType() {
+  void writeAssignmentExpr_nullObjectValuePrimitiveType() {
     Variable variable = Variable.builder().setName("x").setType(TypeNode.INT).build();
     VariableExpr variableExpr =
         VariableExpr.builder().setVariable(variable).setIsDecl(true).build();
@@ -102,7 +102,7 @@ public void writeAssignmentExpr_nullObjectValuePrimitiveType() {
   }
 
   @Test
-  public void writeAssignmentExpr_primitiveToBoxedType() {
+  void writeAssignmentExpr_primitiveToBoxedType() {
     // [Constructing] `Boolean x = (boolean) true`
     Variable variable = Variable.builder().setName("x").setType(TypeNode.BOOLEAN_OBJECT).build();
     VariableExpr variableExpr =
@@ -114,7 +114,7 @@ public void writeAssignmentExpr_primitiveToBoxedType() {
   }
 
   @Test
-  public void writeAssignmentExpr_boxedToPrimitiveType() {
+  void writeAssignmentExpr_boxedToPrimitiveType() {
     // [Constructing] `double x = (Double) y`
     Variable lVariable = Variable.builder().setName("x").setType(TypeNode.DOUBLE).build();
     VariableExpr lVariableExpr =
@@ -126,7 +126,7 @@ public void writeAssignmentExpr_boxedToPrimitiveType() {
   }
 
   @Test
-  public void writeAssignmentExpr_invalidBoxedPrimitiveType() {
+  void writeAssignmentExpr_invalidBoxedPrimitiveType() {
     // [Constructing] `double x = (Integer) y`
     Variable lVariable = Variable.builder().setName("x").setType(TypeNode.DOUBLE).build();
     VariableExpr lVariableExpr =
@@ -138,7 +138,7 @@ public void writeAssignmentExpr_invalidBoxedPrimitiveType() {
   }
 
   @Test
-  public void writeAssignmentExpr_validIsDeclFinalVariableExpr() {
+  void writeAssignmentExpr_validIsDeclFinalVariableExpr() {
     Variable lVariable = Variable.builder().setName("x").setType(TypeNode.INT).build();
     VariableExpr lVariableExpr =
         VariableExpr.builder().setVariable(lVariable).setIsDecl(true).setIsFinal(true).build();
@@ -149,7 +149,7 @@ public void writeAssignmentExpr_validIsDeclFinalVariableExpr() {
   }
 
   @Test
-  public void writeAssignmentExpr_invalidIsNotDeclFinalVariableExpr() {
+  void writeAssignmentExpr_invalidIsNotDeclFinalVariableExpr() {
     Variable lVariable = Variable.builder().setName("x").setType(TypeNode.INT).build();
     VariableExpr lVariableExpr =
         VariableExpr.builder().setVariable(lVariable).setIsDecl(false).setIsFinal(true).build();