only load tests if dependent classes are on the classpath (#3)

src/main/kotlin/io/cloudflight/cleancode/archunit/CleanCodeRuleSets.kt

@@ -1,20 +1,26 @@
 package io.cloudflight.cleancode.archunit
 
 import com.tngtech.archunit.junit.ArchTest
-import com.tngtech.archunit.junit.ArchTests
-import io.cloudflight.cleancode.archunit.rules.jpa.JpaRuleSet
 import io.cloudflight.cleancode.archunit.rules.jdk.JdkRuleSet
+import io.cloudflight.cleancode.archunit.rules.jpa.JpaRuleSet
 import io.cloudflight.cleancode.archunit.rules.logging.LoggingRuleSet
+import io.cloudflight.cleancode.archunit.utils.ruleSetOf
 
 class CleanCodeRuleSets {
 
     @ArchTest
-    val jpa = ArchTests.`in`(JpaRuleSet::class.java)
+    val jpa = ruleSetOf(
+        JpaRuleSet::class.java,
+        requiredClasses = arrayOf(
+            "javax.persistence.Entity",
+            "javax.validation.constraints.NotNull"
+        )
+    )
 
     @ArchTest
-    val logging = ArchTests.`in`(LoggingRuleSet::class.java)
+    val logging = ruleSetOf(LoggingRuleSet::class.java)
 
     @ArchTest
-    val jdk = ArchTests.`in`(JdkRuleSet::class.java)
+    val jdk = ruleSetOf(JdkRuleSet::class.java)
 
 }

src/main/kotlin/io/cloudflight/cleancode/archunit/utils/ClassUtils.kt

@@ -1,10 +1,31 @@
 package io.cloudflight.cleancode.archunit.utils
 
+import com.tngtech.archunit.junit.ArchTests
+
 fun Class<*>.isKotlinClass(): Boolean {
     return this.declaredAnnotations.any {
         it.annotationClass == Metadata::class
     }
 }
 
+internal fun ruleSetOf(clazz: Class<*>, vararg requiredClasses: String): ArchTests {
+    return if (classesExistOnClasspath(*requiredClasses)) {
+        ArchTests.`in`(clazz)
+    } else {
+        ArchTests.`in`(Object::class.java)
+    }
+}
+
+internal fun classesExistOnClasspath(vararg classes: String): Boolean {
+    classes.forEach {
+        try {
+            Class.forName(it)
+        } catch (err: ClassNotFoundException) {
+            return false
+        }
+    }
+    return true
+}
+
 
 

src/test/kotlin/io/cloudflight/cleancode/archunit/utils/ClassUtilsTest.kt

@@ -0,0 +1,23 @@
+package io.cloudflight.cleancode.archunit.utils
+
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+
+class ClassUtilsTest {
+
+    @Test
+    fun existOnClassPath() {
+        assertThat(classesExistOnClasspath("java.lang.Object")).isTrue
+    }
+
+    @Test
+    fun dontExistOnClassPath() {
+        assertThat(classesExistOnClasspath("io.cloudflight.Foo")).isFalse
+    }
+
+    @Test
+    fun dontExistOnClassPath2() {
+        assertThat(classesExistOnClasspath("java.lang.Object", "io.cloudflight.Foo")).isFalse
+    }
+
+}