Optional matchers

Author: seregamorph

hamcrest/src/main/java/org/hamcrest/optional/OptionalEmpty.java

@@ -0,0 +1,25 @@
+package org.hamcrest.optional;
+
+import org.hamcrest.Description;
+import org.hamcrest.TypeSafeDiagnosingMatcher;
+
+import java.util.Optional;
+
+/**
+ * Matcher that expects empty {@link Optional}.
+
+ * @param <T>
+ */
+public class OptionalEmpty<T> extends TypeSafeDiagnosingMatcher<Optional<T>> {
+
+    @Override
+    protected boolean matchesSafely(Optional<T> value, Description mismatchDescription) {
+        mismatchDescription.appendText("is " + value);
+        return !value.isPresent();
+    }
+
+    @Override
+    public void describeTo(Description description) {
+        description.appendText("empty");
+    }
+}

hamcrest/src/main/java/org/hamcrest/optional/OptionalMatchers.java

@@ -0,0 +1,37 @@
+package org.hamcrest.optional;
+
+import org.hamcrest.Matcher;
+
+import java.util.Optional;
+
+/**
+ * Matchers for {@link Optional}.
+ */
+public class OptionalMatchers {
+
+    /**
+     * Matcher for {@link Optional} that expects that value is present.
+     */
+    public static <T> Matcher<Optional<T>> optionalWithValue() {
+        return new OptionalWithValue<>();
+    }
+
+    /**
+     * Matcher for {@link Optional} that expects that it presents and applies passed <code>matcher</code>
+     *
+     * @param matcher matcher to validate present optional value
+     */
+    public static <T> Matcher<Optional<T>> optionalWithValue(Matcher<T> matcher) {
+        return new OptionalWithMatchingValue<>(matcher);
+    }
+
+    /**
+     * Matcher that expects empty optional.
+     */
+    public static <T> Matcher<Optional<T>> emptyOptional() {
+        return new OptionalEmpty<>();
+    }
+
+    private OptionalMatchers() {
+    }
+}

hamcrest/src/main/java/org/hamcrest/optional/OptionalWithMatchingValue.java

@@ -0,0 +1,33 @@
+package org.hamcrest.optional;
+
+import org.hamcrest.Description;
+import org.hamcrest.Matcher;
+import org.hamcrest.TypeSafeDiagnosingMatcher;
+
+import java.util.Optional;
+
+/**
+ * Matcher for {@link Optional} that expects that value is present and matches the given matcher.
+ *
+ * @param <T>
+ */
+public class OptionalWithMatchingValue<T> extends TypeSafeDiagnosingMatcher<Optional<T>> {
+
+    private final Matcher<T> matcher;
+
+    public OptionalWithMatchingValue(Matcher<T> matcher) {
+        this.matcher = matcher;
+    }
+
+    @Override
+    protected boolean matchesSafely(Optional<T> value, Description mismatchDescription) {
+        mismatchDescription.appendText("is " + value);
+        return value.isPresent() && matcher.matches(value.get());
+    }
+
+    @Override
+    public void describeTo(Description description) {
+        description.appendText("present and matches ")
+                .appendDescriptionOf(matcher);
+    }
+}

hamcrest/src/main/java/org/hamcrest/optional/OptionalWithValue.java

@@ -0,0 +1,25 @@
+package org.hamcrest.optional;
+
+import org.hamcrest.Description;
+import org.hamcrest.TypeSafeDiagnosingMatcher;
+
+import java.util.Optional;
+
+/**
+ * Matcher for {@link Optional} that expects that value is present.
+ *
+ * @param <T>
+ */
+public class OptionalWithValue<T> extends TypeSafeDiagnosingMatcher<Optional<T>> {
+
+    @Override
+    protected boolean matchesSafely(Optional<T> value, Description mismatchDescription) {
+        mismatchDescription.appendText("is " + value);
+        return value.isPresent();
+    }
+
+    @Override
+    public void describeTo(Description description) {
+        description.appendText("present");
+    }
+}

hamcrest/src/test/java/org/hamcrest/optional/OptionalMatchersTest.java

@@ -0,0 +1,76 @@
+package org.hamcrest.optional;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.not;
+import static org.hamcrest.optional.OptionalMatchers.emptyOptional;
+import static org.hamcrest.optional.OptionalMatchers.optionalWithValue;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import java.util.Optional;
+
+import org.junit.Test;
+
+public class OptionalMatchersTest {
+
+    @Test
+    public void checkEmptyOptional() {
+        assertThat(Optional.empty(), is(emptyOptional()));
+        assertThat(Optional.of(1), not(emptyOptional()));
+    }
+
+    @Test
+    public void checkEmptyOptionalIsFailure() {
+        AssertionError failure = assertThrows(AssertionError.class, () -> {
+            assertThat(Optional.of(1), is(emptyOptional()));
+        });
+        assertEquals("\n" +
+                "Expected: is empty\n" +
+                "     but: is Optional[1]", failure.getMessage());
+    }
+
+    @Test
+    public void checkEmptyOptionalFailure() {
+        AssertionError failure = assertThrows(AssertionError.class, () -> {
+            assertThat(Optional.of(1), emptyOptional());
+        });
+        assertEquals("\n" +
+                "Expected: empty\n" +
+                "     but: is Optional[1]", failure.getMessage());
+    }
+
+    @Test
+    public void checkWithValue() {
+        assertThat(Optional.empty(), not(optionalWithValue()));
+        assertThat(Optional.of(1), is(optionalWithValue()));
+    }
+
+    @Test
+    public void checkWithMatchingValue() {
+        assertThat(Optional.empty(), not(optionalWithValue(equalTo(1))));
+        assertThat(Optional.of(1), is(optionalWithValue(equalTo(1))));
+        assertThat(Optional.of(1), not(optionalWithValue(equalTo(1L))));
+    }
+
+    @Test
+    public void checkWithValueFailure() {
+        AssertionError failure = assertThrows(AssertionError.class, () -> {
+            assertThat(Optional.empty(), is(optionalWithValue()));
+        });
+        assertEquals("\n" +
+                "Expected: is present\n" +
+                "     but: is Optional.empty", failure.getMessage());
+    }
+
+    @Test
+    public void checkWithMatchingValueFailure() {
+        AssertionError failure = assertThrows(AssertionError.class, () -> {
+            assertThat(Optional.empty(), is(optionalWithValue(equalTo(1))));
+        });
+        assertEquals("\n" +
+                "Expected: is present and matches <1>\n" +
+                "     but: is Optional.empty", failure.getMessage());
+    }
+}