test: add a test case for studying the reflection methods: `Class.get…

…Methods` and `Class.getDeclaredMethods`

src/test/java/io/foldright/inspectablewrappers/study/MethodsOfInterfaceStudyTest.kt

@@ -0,0 +1,72 @@
+package io.foldright.inspectablewrappers.study
+
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.inspectors.shouldForAll
+import io.kotest.matchers.collections.shouldBeEmpty
+import io.kotest.matchers.collections.shouldContainExactlyInAnyOrder
+import java.lang.reflect.Method
+import java.lang.reflect.Modifier
+
+/**
+ * a test case for studying the reflection methods: [Class.getMethods] and [Class.getDeclaredMethods]
+ */
+class MethodsOfInterfaceStudyTest : FunSpec({
+    test("Methods of Interface") {
+        // methods of interface do not contain the methods of Object
+        I0::class.java.methods.shouldBeEmpty()
+        I0::class.java.declaredMethods.shouldBeEmpty()
+
+        listOf(I1::class.java.methods, I1::class.java.declaredMethods).shouldForAll { methods ->
+            methods.toNames().shouldContainExactlyInAnyOrder("foo")
+            methods.filter { it.isAbstract }.toNames().shouldContainExactlyInAnyOrder("foo")
+        }
+
+        listOf(I2::class.java.methods, I2::class.java.declaredMethods).shouldForAll { methods ->
+            methods.toNames().shouldContainExactlyInAnyOrder("foo", "bar")
+            // default methods is NOT abstract
+            methods.filter { it.isAbstract }.toNames().shouldContainExactlyInAnyOrder("foo")
+            // also otherwise
+            methods.filter { it.isDefault }.toNames().shouldContainExactlyInAnyOrder("bar")
+        }
+
+        // `getMethods()` CONTAIN the method of base interface
+        I12::class.java.methods.apply {
+            toNames().shouldContainExactlyInAnyOrder("foo", "bar", "bar2")
+            filter { it.isAbstract }.toNames().shouldContainExactlyInAnyOrder("foo", "bar2")
+            filter { it.isDefault }.toNames().shouldContainExactlyInAnyOrder("bar")
+        }
+        // `getDeclaredMethods()` do NOT CONTAIN the method of base interface
+        I12::class.java.declaredMethods.apply {
+            toNames().shouldContainExactlyInAnyOrder("bar", "bar2")
+            filter { it.isAbstract }.toNames().shouldContainExactlyInAnyOrder("bar2")
+            filter { it.isDefault }.toNames().shouldContainExactlyInAnyOrder("bar")
+        }
+    }
+})
+
+
+interface I0
+
+@Suppress("unused")
+interface I1 {
+    fun foo()
+}
+
+@Suppress("unused")
+interface I2 {
+    fun foo()
+
+    fun bar() = 42
+}
+
+@Suppress("unused")
+interface I12 : I1 {
+    fun bar() = 42
+
+    fun bar2()
+}
+
+fun Array<Method>.toNames() = map { it.name }
+fun Iterable<Method>.toNames() = map { it.name }
+val Method.isAbstract get() = Modifier.isAbstract(modifiers)
+