1 files changed, 98 insertions, 0 deletions
diff --git a/src/test/java/au/id/zancanaro/javacheck/OptionalRulesTest.java b/src/test/java/au/id/zancanaro/javacheck/OptionalRulesTest.java
new file mode 100644
index 0000000..407ffbd
--- /dev/null
+++ b/src/test/java/au/id/zancanaro/javacheck/OptionalRulesTest.java
@@ -0,0 +1,98 @@
+package au.id.zancanaro.javacheck;
+
+import au.id.zancanaro.javacheck.annotations.DataSource;
+import au.id.zancanaro.javacheck.annotations.Property;
+import au.id.zancanaro.javacheck.junit.Properties;
+import org.junit.runner.RunWith;
+
+import java.util.Optional;
+import java.util.function.Function;
+
+import static au.id.zancanaro.javacheck.Generator.pure;
+import static au.id.zancanaro.javacheck.Generators.integer;
+import static au.id.zancanaro.javacheck.Generators.oneOf;
+import static org.junit.Assert.assertEquals;
+
+@RunWith(Properties.class)
+public class OptionalRulesTest {
+
+    @DataSource
+    public static Generator<Optional<Integer>> listOfIntegers = oneOf(
+            pure(Optional.empty()),
+            integer().map(Optional::of));
+
+    @DataSource
+    public static Generator<Function<Integer, Integer>> integerFunction =
+            oneOf(
+                    integer().map(OptionalRulesTest::plusI),
+                    integer().map(OptionalRulesTest::timesI),
+                    integer().map(OptionalRulesTest::constantlyI));
+
+    @Property
+    public void flatMapIdentity(Optional<Integer> optional) {
+        assertEquals(optional, optional.flatMap(Optional::of));
+    }
+
+    @Property
+    public void mappingComposition(
+            Optional<Integer> optional,
+            Function<Integer, Integer> f,
+            Function<Integer, Integer> g) {
+        Optional<Integer> left = optional
+                .map(g)
+                .map(f);
+
+        Optional<Integer> right = optional
+                .map(x -> f.apply(g.apply(x)));
+
+        assertEquals(left, right);
+    }
+
+    @Property
+    public void mapIdentityIsIdentity(Optional<Integer> optional) {
+        Optional<Integer> mapped = optional.map(x -> x);
+
+        assertEquals(optional, mapped);
+    }
+
+    private static Function<Integer,Integer> plusI(final int i) {
+        return new Function<Integer, Integer>() {
+            @Override
+            public Integer apply(Integer integer) {
+                return i + integer;
+            }
+
+            @Override
+            public String toString() {
+                return "x -> x + " + i;
+            }
+        };
+    }
+
+    private static Function<Integer,Integer> timesI(final int i) {
+        return new Function<Integer, Integer>() {
+            @Override
+            public Integer apply(Integer integer) {
+                return i * integer;
+            }
+
+            @Override
+            public String toString() {
+                return "x -> x * " + i;
+            }
+        };
+    }
+    private static Function<Integer,Integer> constantlyI(final int i) {
+        return new Function<Integer, Integer>() {
+            @Override
+            public Integer apply(Integer integer) {
+                return i;
+            }
+
+            @Override
+            public String toString() {
+                return "x -> " + i;
+            }
+        };
+    }
+}