Worked on TODOs in SharedFileChannelTest

* Now testing for correct exception thrown from write and read

main/commons-test/src/main/java/org/cryptomator/common/test/matcher/ExceptionMatcher.java

@@ -0,0 +1,48 @@
+package org.cryptomator.common.test.matcher;
+
+import java.util.Optional;
+
+import org.hamcrest.Description;
+import org.hamcrest.Matcher;
+import org.hamcrest.TypeSafeDiagnosingMatcher;
+
+public class ExceptionMatcher<T extends Throwable> extends TypeSafeDiagnosingMatcher<T> {
+
+	public static <T extends Throwable> ExceptionMatcher<T> ofType(Class<T> exceptionType) {
+		return new ExceptionMatcher<>(exceptionType);
+	}
+
+	private final Class<T> exceptionType;
+	private final Optional<Matcher<T>> subMatcher;
+
+	private ExceptionMatcher(Class<T> exceptionType) {
+		super(exceptionType);
+		this.exceptionType = exceptionType;
+		this.subMatcher = Optional.empty();
+	}
+
+	private ExceptionMatcher(Class<T> exceptionType, Matcher<T> subMatcher) {
+		super(exceptionType);
+		this.exceptionType = exceptionType;
+		this.subMatcher = Optional.of(subMatcher);
+	}
+
+	@Override
+	public void describeTo(Description description) {
+		subMatcher.ifPresent(description::appendDescriptionOf);
+	}
+
+	@Override
+	protected boolean matchesSafely(T item, Description mismatchDescription) {
+		if (subMatcher.map(matcher -> !matcher.matches(item)).orElse(false)) {
+			subMatcher.get().describeMismatch(item, mismatchDescription);
+			return false;
+		}
+		return true;
+	}
+
+	public Matcher<T> withCauseThat(Matcher<? super Throwable> matcher) {
+		return new ExceptionMatcher<T>(exceptionType, new PropertyMatcher<>(exceptionType, Throwable::getCause, "cause", matcher));
+	}
+
+}

main/commons-test/src/main/java/org/cryptomator/common/test/matcher/PropertyMatcher.java

@@ -14,11 +14,11 @@ import org.hamcrest.TypeSafeDiagnosingMatcher;
 public class PropertyMatcher<T, P> extends TypeSafeDiagnosingMatcher<T> {
 
 	private final Class<T> expectedType;
-	private final Function<T, P> getter;
+	private final Function<? super T, P> getter;
 	private final String name;
 	private final Matcher<? super P> subMatcher;
 
-	public PropertyMatcher(Class<T> type, Function<T, P> getter, String name, Matcher<? super P> subMatcher) {
+	public PropertyMatcher(Class<T> type, Function<? super T, P> getter, String name, Matcher<? super P> subMatcher) {
 		super(type);
 		this.expectedType = type;
 		this.getter = getter;
@@ -32,7 +32,7 @@ public class PropertyMatcher<T, P> extends TypeSafeDiagnosingMatcher<T> {
 				.appendText(expectedType.getSimpleName()) //
 				.appendText(" with a ") //
 				.appendText(name) //
-				.appendText(" that is ") //
+				.appendText(" that ") //
 				.appendDescriptionOf(subMatcher);
 	}
 
@@ -46,7 +46,7 @@ public class PropertyMatcher<T, P> extends TypeSafeDiagnosingMatcher<T> {
 					.appendText(expectedType.getSimpleName()) //
 					.appendText(" with a ") //
 					.appendText(name) //
-					.appendText(" that was ");
+					.appendText(" that ");
 			subMatcher.describeMismatch(propertyValue, mismatchDescription);
 			return false;
 		}

main/filesystem-nio/src/test/java/org/cryptomator/filesystem/nio/SharedFileChannelTest.java

@@ -2,8 +2,8 @@ package org.cryptomator.filesystem.nio;
 
 import static java.lang.String.format;
 import static org.apache.commons.lang3.concurrent.ConcurrentUtils.constantFuture;
+import static org.cryptomator.common.test.matcher.ExceptionMatcher.ofType;
 import static org.cryptomator.filesystem.nio.SharedFileChannel.EOF;
-import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertThat;
 import static org.mockito.Mockito.doThrow;
@@ -262,12 +262,13 @@ public class SharedFileChannelTest {
 		public void testReadFullyWrapsExceptionFromReadInUncheckedIOException() throws InterruptedException, ExecutionException {
 			ByteBuffer buffer = ByteBuffer.allocate(0);
 			ExecutionException exceptionFromRead = new ExecutionException(new IOException());
+			@SuppressWarnings("unchecked")
 			Future<Integer> result = mock(Future.class);
 			when(channel.read(buffer, 0)).thenReturn(result);
 			when(result.get()).thenThrow(exceptionFromRead);
 
 			thrown.expect(UncheckedIOException.class);
-			thrown.expectCause(is(instanceOf(IOException.class))); // TODO check correct cause of cause
+			thrown.expectCause(is(ofType(IOException.class).withCauseThat(is(exceptionFromRead))));
 
 			inTest.readFully(0, buffer);
 		}
@@ -555,12 +556,13 @@ public class SharedFileChannelTest {
 			int position = 0;
 			ByteBuffer buffer = ByteBuffer.allocate(count);
 			ExecutionException exceptionFromWrite = new ExecutionException(new IOException());
+			@SuppressWarnings("unchecked")
 			Future<Integer> result = mock(Future.class);
 			when(channel.write(buffer, position)).thenReturn(result);
 			when(result.get()).thenThrow(exceptionFromWrite);
 
 			thrown.expect(UncheckedIOException.class);
-			thrown.expectCause(is(instanceOf(IOException.class))); // TODO check correct cause of cause
+			thrown.expectCause(is(ofType(IOException.class).withCauseThat(is(exceptionFromWrite))));
 
 			inTest.writeFully(position, buffer);
 		}