improve rule to not fail for classes with no tests in their packages (#1368)

This will improve the existing rule to test that test classes reside in
the same package as their implementation. In particular the rule:

Should not fail if there are multiple test classes with the same simple
name and some of the classes have no tests at all

Issue: #1367

Author: hankem

archunit/src/main/java/com/tngtech/archunit/library/GeneralCodingRules.java

@@ -452,12 +452,16 @@ public static ArchRule testClassesShouldResideInTheSamePackageAsImplementation(S
     private static ArchCondition<JavaClass> resideInTheSamePackageAsTheirTestClasses(String testClassSuffix) {
         return new ArchCondition<JavaClass>("reside in the same package as their test classes") {
             Map<String, List<JavaClass>> testClassesBySimpleClassName = new HashMap<>();
+            Map<String, List<JavaClass>> classesByPackageName = new HashMap<>();
 
             @Override
             public void init(Collection<JavaClass> allClasses) {
                 testClassesBySimpleClassName = allClasses.stream()
                         .filter(clazz -> clazz.getName().endsWith(testClassSuffix))
                         .collect(groupingBy(JavaClass::getSimpleName));
+
+                classesByPackageName = allClasses.stream()
+                        .collect(groupingBy(JavaClass::getPackageName));
             }
 
             @Override
@@ -468,7 +472,8 @@ public void check(JavaClass implementationClass, ConditionEvents events) {
                 List<JavaClass> possibleTestClasses = testClassesBySimpleClassName.getOrDefault(possibleTestClassName, emptyList());
 
                 boolean isTestClassInWrongPackage = !possibleTestClasses.isEmpty()
-                        && possibleTestClasses.stream().noneMatch(clazz -> clazz.getPackageName().equals(implementationClassPackageName));
+                        && possibleTestClasses.stream().noneMatch(clazz -> clazz.getPackageName().equals(implementationClassPackageName))
+                        && !allPossibleTestClassesHaveImplementationInRightPackage(possibleTestClasses);
 
                 if (isTestClassInWrongPackage) {
                     possibleTestClasses.forEach(wrongTestClass -> {
@@ -478,6 +483,13 @@ public void check(JavaClass implementationClass, ConditionEvents events) {
                     });
                 }
             }
+
+            private boolean allPossibleTestClassesHaveImplementationInRightPackage(List<JavaClass> possibleTestClasses) {
+                return possibleTestClasses.stream()
+                        .allMatch(testClazz -> classesByPackageName.getOrDefault(testClazz.getPackageName(), emptyList())
+                                .stream()
+                                 .anyMatch(clazz -> testClazz.getSimpleName().equals(clazz.getSimpleName() + testClassSuffix)));
+            }
         };
     }
 

archunit/src/test/java/com/tngtech/archunit/library/GeneralCodingRulesTest.java

@@ -5,6 +5,7 @@
 import com.tngtech.archunit.library.testclasses.packages.correct.defaultsuffix.ImplementationClassWithCorrectPackage;
 import com.tngtech.archunit.library.testclasses.packages.correct.notest.ImplementationClassWithoutTestClass;
 import com.tngtech.archunit.library.testclasses.packages.correct.onedirmatching.ImplementationClassWithOneTestPackageMatchingOutOfTwo;
+import com.tngtech.archunit.library.testclasses.packages.correct.twoimplementationsonetestdir1.SimpleNameThatOccursInSeveralPackages;
 import com.tngtech.archunit.library.testclasses.packages.incorrect.nodirmatching.ImplementationClassWithMultipleTestsNotMatchingImplementationClassPackage;
 import com.tngtech.archunit.library.testclasses.packages.incorrect.wrongsubdir.customsuffix.ImplementationClassWithWrongTestClassPackageCustomSuffix;
 import com.tngtech.archunit.library.testclasses.packages.incorrect.wrongsubdir.customsuffix.subdir.ImplementationClassWithWrongTestClassPackageCustomSuffixTestingScenario;
@@ -89,6 +90,16 @@ public void should_not_pass_when_none_of_multiple_matching_test_classes_resides_
                 );
     }
 
+    @Test
+    public void should_pass_when_only_one_of_two_implementations_have_test_class_and_it_is_in_implementation_package() {
+        assertThatRule(testClassesShouldResideInTheSamePackageAsImplementation())
+                .checking(new ClassFileImporter().importPackagesOf(
+                        SimpleNameThatOccursInSeveralPackages.class,
+                        com.tngtech.archunit.library.testclasses.packages.incorrect.twoimplementationsonetestdir2.SimpleNameThatOccursInSeveralPackages.class
+                ))
+                .hasNoViolation();
+    }
+
     @Test
     public void ASSERTIONS_SHOULD_HAVE_DETAIL_MESSAGE_should_fail_on_assert_without_detail_message() {
         @SuppressWarnings("unused")

archunit/src/test/java/com/tngtech/archunit/library/testclasses/packages/correct/twoimplementationsonetestdir1/SimpleNameThatOccursInSeveralPackages.java

@@ -0,0 +1,4 @@
+package com.tngtech.archunit.library.testclasses.packages.correct.twoimplementationsonetestdir1;
+
+public class SimpleNameThatOccursInSeveralPackages {
+}

archunit/src/test/java/com/tngtech/archunit/library/testclasses/packages/correct/twoimplementationsonetestdir1/SimpleNameThatOccursInSeveralPackagesTest.java

@@ -0,0 +1,4 @@
+package com.tngtech.archunit.library.testclasses.packages.correct.twoimplementationsonetestdir1;
+
+class SimpleNameThatOccursInSeveralPackagesTest {
+}

archunit/src/test/java/com/tngtech/archunit/library/testclasses/packages/incorrect/twoimplementationsonetestdir2/SimpleNameThatOccursInSeveralPackages.java

@@ -0,0 +1,4 @@
+package com.tngtech.archunit.library.testclasses.packages.incorrect.twoimplementationsonetestdir2;
+
+public class SimpleNameThatOccursInSeveralPackages {
+}