Add test that generated invalid code (#331)

* Add test that generated invalid code

* Whitelist the case where assertThrows can be rewritten

A check is added to see if assertThrows appears immediately inside
a J.Block.

* Add degenerate test case showing we need to check for J.Block

* Link to PR for background

---------

Co-authored-by: Tim te Beek <[email protected]>

Author: Meijuh

src/main/java/org/openrewrite/java/testing/assertj/JUnitAssertThrowsToAssertExceptionType.java

@@ -72,7 +72,9 @@ private Supplier<JavaParser> assertionsParser(ExecutionContext ctx) {
         @Override
         public J.MethodInvocation visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx) {
             J.MethodInvocation mi = super.visitMethodInvocation(method, ctx);
-            if (ASSERT_THROWS_MATCHER.matches(mi) && mi.getArguments().size() == 2) {
+            if (ASSERT_THROWS_MATCHER.matches(mi)
+              && mi.getArguments().size() == 2
+              && getCursor().getParentTreeCursor().getValue() instanceof J.Block) {
                 J executable = mi.getArguments().get(1);
                 if (executable instanceof J.Lambda) {
                     executable = ((J.Lambda) executable).withType(THROWING_CALLABLE_TYPE);

src/test/java/org/openrewrite/java/testing/assertj/JUnitAssertThrowsToAssertExceptionTypeTest.java

@@ -17,6 +17,7 @@
 
 import org.junit.jupiter.api.Test;
 import org.openrewrite.InMemoryExecutionContext;
+import org.openrewrite.Issue;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
 import org.openrewrite.test.RewriteTest;
@@ -98,4 +99,52 @@ public void throwsWithMemberReference() {
           )
         );
     }
+
+    @Test
+    @Issue("https://github.com/openrewrite/rewrite-testing-frameworks/pull/331")
+    void assertThrowsAssignment() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              import static org.junit.jupiter.api.Assertions.assertThrows;
+
+              public class SimpleExpectedExceptionTest {
+                  public void throwsExceptionWithSpecificType() {
+                      NullPointerException npe = assertThrows(NullPointerException.class, () -> {
+                          throw new NullPointerException();
+                      });
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    /**
+     * A degenerate case showing we need to make sure the <code>assertThrows</code> appears
+     * immediately inside a J.Block.
+     */
+    @Test
+    @Issue("https://github.com/openrewrite/rewrite-testing-frameworks/pull/331")
+    void assertThrowsTernaryAssignment() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              import static org.junit.jupiter.api.Assertions.assertThrows;
+
+              public class SimpleExpectedExceptionTest {
+                  public void throwsExceptionWithSpecificType() {
+                      NullPointerException npe = hashCode() == 42
+                        ? new NullPointerException()
+                        : assertThrows(NullPointerException.class, () -> {
+                          throw new NullPointerException();
+                      });
+                  }
+              }
+              """
+          )
+        );
+    }
 }