Add unit test showing null Methodinvocation type

src/test/java/org/openrewrite/java/testing/cleanup/KotlinTestMethodShouldBeUnitTest.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2025 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (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://docs.moderne.io/licensing/moderne-source-available-license
+ * <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.cleanup;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.InMemoryExecutionContext;
+import org.openrewrite.Parser;
+import org.openrewrite.SourceFile;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.kotlin.KotlinIsoVisitor;
+import org.openrewrite.kotlin.KotlinParser;
+import org.openrewrite.test.RewriteTest;
+import org.openrewrite.test.SourceSpec;
+
+import java.nio.file.Path;
+import java.util.Collections;
+import java.util.Iterator;
+
+import static java.util.Collections.singleton;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.openrewrite.kotlin.Assertions.kotlin;
+
+//
+public class KotlinTestMethodShouldBeUnitTest implements RewriteTest {
+
+    @Test
+    void showNullMethodInvocationType() {
+        //language=kotlin
+        SourceSpec<?> source = getOnly(
+          kotlin(
+            """
+              class ExampleTest {
+                  fun myTest() = run {
+                      return 1
+                  }
+              }
+              """
+          ));
+        Parser parser = KotlinParser.builder().build();
+        Path sourcePath = parser.sourcePathFromSourceText(source.getDir(), source.getBefore());
+        ExecutionContext ctx = new InMemoryExecutionContext();
+        Parser.Input input = Parser.Input.fromString(
+          sourcePath, source.getBefore(), parser.getCharset(ctx));
+        SourceFile sourceFile = getOnly(
+          parser.parseInputs(singleton(input), null, ctx).toList());
+        new FindMissingTypesVisitor().visit(sourceFile, ctx);
+    }
+
+    private static class FindMissingTypesVisitor extends KotlinIsoVisitor<ExecutionContext> {
+
+        @Override
+        public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method,
+                                                        ExecutionContext ctx) {
+            assertNotNull(method.getMethodType());
+            return method;
+        }
+    }
+
+    private static <T> T getOnly(Iterable<T> iterable) {
+        Iterator<T> iter = iterable.iterator();
+        T only = iter.next();
+        assertFalse(iter.hasNext());
+        return only;
+    }
+}