Merge pull request #27862 from smoothbear

* pr/27862:
  Polish "Add testing for AbstractFailureAnalyzer.findCause"
  Add testing for AbstractFailureAnalyzer.findCause

Closes gh-27862

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/diagnostics/AbstractFailureAnalyzer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,10 +31,7 @@ public abstract class AbstractFailureAnalyzer<T extends Throwable> implements Fa
 	@Override
 	public FailureAnalysis analyze(Throwable failure) {
 		T cause = findCause(failure, getCauseType());
-		if (cause != null) {
-			return analyze(failure, cause);
-		}
-		return null;
+		return (cause != null) ? analyze(failure, cause) : null;
 	}
 
 	/**

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/diagnostics/AbstractFailureAnalyzerTests.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2012-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.springframework.boot.diagnostics;
+
+import java.io.IOException;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link AbstractFailureAnalyzer}.
+ *
+ * @author Kim Jung Bin
+ * @author Stephane Nicoll
+ */
+class AbstractFailureAnalyzerTests {
+
+	private final TestFailureAnalyzer failureAnalyzer = new TestFailureAnalyzer();
+
+	@Test
+	void findCauseWithNullException() {
+		assertThat(this.failureAnalyzer.findCause(null, Throwable.class)).isNull();
+	}
+
+	@Test
+	void findCauseWithDirectExactMatch() {
+		TestException ex = new TestException();
+		assertThat(this.failureAnalyzer.findCause(ex, TestException.class)).isEqualTo(ex);
+	}
+
+	@Test
+	void findCauseWithDirectSubClass() {
+		SpecificTestException ex = new SpecificTestException();
+		assertThat(this.failureAnalyzer.findCause(ex, TestException.class)).isEqualTo(ex);
+	}
+
+	@Test
+	void findCauseWitNestedAndExactMatch() {
+		TestException ex = new TestException();
+		assertThat(this.failureAnalyzer.findCause(new IllegalArgumentException(new IllegalStateException(ex)),
+				TestException.class)).isEqualTo(ex);
+	}
+
+	@Test
+	void findCauseWitNestedAndSubClass() {
+		SpecificTestException ex = new SpecificTestException();
+		assertThat(this.failureAnalyzer.findCause(new IOException(new IllegalStateException(ex)), TestException.class))
+				.isEqualTo(ex);
+	}
+
+	@Test
+	void findCauseWithUnrelatedException() {
+		IOException ex = new IOException();
+		assertThat(this.failureAnalyzer.findCause(ex, TestException.class)).isNull();
+	}
+
+	@Test
+	void findCauseWithMoreSpecificException() {
+		TestException ex = new TestException();
+		assertThat(this.failureAnalyzer.findCause(ex, SpecificTestException.class)).isNull();
+	}
+
+	static class TestFailureAnalyzer extends AbstractFailureAnalyzer<Throwable> {
+
+		@Override
+		protected FailureAnalysis analyze(Throwable rootFailure, Throwable cause) {
+			return null;
+		}
+
+	}
+
+	static class TestException extends Exception {
+
+	}
+
+	static class SpecificTestException extends TestException {
+
+	}
+
+}