1 files changed, 106 insertions, 0 deletions
diff --git a/src/test/java/au/id/zancanaro/javacheck/SetFunctorRulesTest.java b/src/test/java/au/id/zancanaro/javacheck/SetFunctorRulesTest.java
new file mode 100644
index 0000000..04fa674
--- /dev/null
+++ b/src/test/java/au/id/zancanaro/javacheck/SetFunctorRulesTest.java
@@ -0,0 +1,106 @@
+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.Set;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import static au.id.zancanaro.javacheck.Generators.longInteger;
+import static au.id.zancanaro.javacheck.Generators.oneOf;
+import static org.junit.Assert.assertEquals;
+
+@RunWith(Properties.class)
+public class SetFunctorRulesTest {
+
+    @DataSource
+    public static Generator<Function<Long, Long>> integerFunction =
+            oneOf(
+                    longInteger().map(SetFunctorRulesTest::plusI),
+                    longInteger().map(SetFunctorRulesTest::timesI),
+                    longInteger().map(SetFunctorRulesTest::constantlyI));
+
+    @Property
+    public void mappingCompositionsWithStreams(
+            Set<Long> list,
+            Function<Long, Long> f,
+            Function<Long, Long> g) {
+        Set<Long> left = list.stream()
+                .map(g)
+                .map(f)
+                .collect(Collectors.toSet());
+
+        Set<Long> right = list.stream()
+                .map(f.compose(g))
+                .collect(Collectors.toSet());
+
+        assertEquals(left, right);
+    }
+
+    @Property
+    public void mappingCompositionsWithIntermediateList(
+            Set<Long> list,
+            Function<Long, Long> f,
+            Function<Long, Long> g) {
+        Set<Long> intermediate = list.stream().map(g).collect(Collectors.toSet());
+        Set<Long> left = intermediate.stream().map(f).collect(Collectors.toSet());
+
+        Set<Long> right = list.stream()
+                .map(f.compose(g))
+                .collect(Collectors.toSet());
+
+        assertEquals(left, right);
+    }
+
+    @Property
+    public void mapIdentityIsIdentity(Set<Long> list) {
+        Set<Long> mapped = list.stream().map(x -> x).collect(Collectors.toSet());
+
+        assertEquals(list, mapped);
+    }
+
+    private static Function<Long, Long> plusI(final long i) {
+        return new Function<Long, Long>() {
+            @Override
+            public Long apply(Long integer) {
+                return i + integer;
+            }
+
+            @Override
+            public String toString() {
+                return "x -> x + " + i;
+            }
+        };
+    }
+
+    private static Function<Long, Long> timesI(final long i) {
+        return new Function<Long, Long>() {
+            @Override
+            public Long apply(Long integer) {
+                return i * integer;
+            }
+
+            @Override
+            public String toString() {
+                return "x -> x * " + i;
+            }
+        };
+    }
+
+    private static Function<Long, Long> constantlyI(final long i) {
+        return new Function<Long, Long>() {
+            @Override
+            public Long apply(Long integer) {
+                return i;
+            }
+
+            @Override
+            public String toString() {
+                return "x -> " + i;
+            }
+        };
+    }
+}