root cause finder

core-java-modules/core-java/src/test/java/com/baeldung/exceptions/RootCauseFinderTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.exceptions;
+
+import com.google.common.base.Throwables;
+import org.apache.commons.lang3.exception.ExceptionUtils;
+import org.junit.jupiter.api.Test;
+
+import static com.baeldung.exceptions.RootCauseFinder.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Tests the {@link RootCauseFinder}.
+ */
+public class RootCauseFinderTest {
+
+    @Test
+    public void givenNestedException_whenFindingRootCauseUsingJava_thenRootCauseFound() {
+        try {
+            IntParser.parse("text");
+        } catch (InvalidNumber ex) {
+            assertTrue(findCauseUsingPlainJava(ex) instanceof NumberFormatException);
+        }
+    }
+
+    @Test
+    public void givenNonNestedException_whenFindingRootCauseUsingJava_thenRootCauseFound() {
+        try {
+            IntParser.parse(null);
+        } catch (Exception ex) {
+            assertTrue(findCauseUsingPlainJava(ex) instanceof IllegalArgumentException);
+        }
+    }
+
+    @Test
+    public void givenNestedException_whenFindingRootCauseUsingApacheCommons_thenRootCauseFound() {
+        try {
+            IntParser.parse("text");
+        } catch (InvalidNumber ex) {
+            assertTrue(ExceptionUtils.getRootCause(ex) instanceof NumberFormatException);
+        }
+    }
+
+    @Test
+    public void givenNestedException_whenFindingRootCauseUsingGuava_thenRootCauseFound() {
+        try {
+            IntParser.parse("text");
+        } catch (InvalidNumber ex) {
+            assertTrue(Throwables.getRootCause(ex) instanceof NumberFormatException);
+        }
+    }
+
+}