1 files changed, 50 insertions, 0 deletions
diff --git a/src/main/java/org/junit/internal/matchers/ThrowableCauseMatcher.java b/src/main/java/org/junit/internal/matchers/ThrowableCauseMatcher.java
new file mode 100644
index 0000000..22ce8bd
--- /dev/null
+++ b/src/main/java/org/junit/internal/matchers/ThrowableCauseMatcher.java
@@ -0,0 +1,50 @@
+package org.junit.internal.matchers;
+
+import org.hamcrest.Description;
+import org.hamcrest.Factory;
+import org.hamcrest.Matcher;
+import org.hamcrest.TypeSafeMatcher;
+
+/**
+ * A matcher that applies a delegate matcher to the cause of the current Throwable, returning the result of that
+ * match.
+ *
+ * @param <T> the type of the throwable being matched
+ */
+public class ThrowableCauseMatcher<T extends Throwable> extends
+        TypeSafeMatcher<T> {
+
+    private final Matcher<? extends Throwable> causeMatcher;
+
+    public ThrowableCauseMatcher(Matcher<? extends Throwable> causeMatcher) {
+        this.causeMatcher = causeMatcher;
+    }
+
+    public void describeTo(Description description) {
+        description.appendText("exception with cause ");
+        description.appendDescriptionOf(causeMatcher);
+    }
+
+    @Override
+    protected boolean matchesSafely(T item) {
+        return causeMatcher.matches(item.getCause());
+    }
+
+    @Override
+    protected void describeMismatchSafely(T item, Description description) {
+        description.appendText("cause ");
+        causeMatcher.describeMismatch(item.getCause(), description);
+    }
+
+    /**
+     * Returns a matcher that verifies that the outer exception has a cause for which the supplied matcher
+     * evaluates to true.
+     *
+     * @param matcher to apply to the cause of the outer exception
+     * @param <T> type of the outer exception
+     */
+    @Factory
+    public static <T extends Throwable> Matcher<T> hasCause(final Matcher<? extends Throwable> matcher) {
+        return new ThrowableCauseMatcher<T>(matcher);
+    }
+}
+\ No newline at end of file