Change KiwiXmlAssertTest assertions to check for instanceof Assertion…

…Error

okhttp3.mockwebserver in version 4.12.0 depends on JUnit 4 (because
MockWebServer actually extends ExternalResource). This caused some
tests in KiwiXmlAssertTest to fail because they were expecting errors to
be exactly instance of AssertionError. But xmlunit-assertj (deep inside
org.xmlunit.assertj.error.ComparisonFailureErrorFactory) actually changes
the error it throws to be an org,junit.ComparisonFailure if that class is
available at runtime, whereas it simply delegates to AssertJ and throws a
regular AssertionError if it is not available. So, by mockwebserver
depending on JUnit 4.x, it makes ComparisonFailure available on the
class path, so the throwable changes to ComparisonFailure instead of
a raw AssertionError. ComparisonFailure is a subclass of AssertionError
so we can fix it by changing our assertions in KiwiXmlAssertTest to
only check that a Throwable is an instance of (not exactly) AssertionError,
so it will pass whether ComparisonFailure exists or not.

I don't know for sure, but am guessing they have to do it this way
for JUnit 4.x environments to work properly. But I'm not at all sure.

src/test/java/org/kiwiproject/test/xmlunit/KiwiXmlAssertTest.java

@@ -50,7 +50,7 @@ void shouldAcceptTestNameAsString() {
                             .withTestName("custom-test-name")
                             .and(otherXml)
                             .areIdentical())
-                    .isExactlyInstanceOf(AssertionError.class);
+                    .isInstanceOf(AssertionError.class);
         }
 
         @Test
@@ -63,7 +63,7 @@ void shouldAcceptTestNameFromTestInfo(TestInfo testInfo) {
                             .withTestNameFrom(testInfo)
                             .and(otherXml)
                             .areIdentical())
-                    .isExactlyInstanceOf(AssertionError.class);
+                    .isInstanceOf(AssertionError.class);
         }
     }
 
@@ -108,7 +108,7 @@ void shouldThrowAssertionErrorWhenXmlIsDifferent() {
 
                 assertThatThrownBy(() ->
                         KiwiXmlAssert.assertThat(xml).isIdenticalTo(otherXml))
-                        .isExactlyInstanceOf(AssertionError.class);
+                        .isInstanceOf(AssertionError.class);
             }
         }
 
@@ -136,7 +136,7 @@ void shouldThrowAssertionErrorWhenXmlIsDifferent() {
 
                 assertThatThrownBy(() ->
                         KiwiXmlAssert.assertThat(xml).isIdenticalToIgnoringWhitespace(otherXml))
-                        .isExactlyInstanceOf(AssertionError.class);
+                        .isInstanceOf(AssertionError.class);
             }
         }
 
@@ -165,7 +165,7 @@ void canaryDoesNotIgnoreCommentsBetweenTags() {
 
                 assertThatThrownBy(() ->
                         KiwiXmlAssert.assertThat(xml).isIdenticalToIgnoringComments(otherXml))
-                        .isExactlyInstanceOf(AssertionError.class);
+                        .isInstanceOf(AssertionError.class);
             }
         }
 
@@ -189,7 +189,7 @@ void shouldThrowAssertionErrorWhenXmlIsDifferent() {
 
                 assertThatThrownBy(() ->
                         KiwiXmlAssert.assertThat(xml).isIdenticalToIgnoringWhitespaceAndComments(otherXml))
-                        .isExactlyInstanceOf(AssertionError.class);
+                        .isInstanceOf(AssertionError.class);
             }
         }
     }