6 files changed, 161 insertions, 24 deletions
diff --git a/src/main/java/au/id/zancanaro/javacheck/Generators.java b/src/main/java/au/id/zancanaro/javacheck/Generators.java
index af8f8ad..631e14a 100644
--- a/src/main/java/au/id/zancanaro/javacheck/Generators.java
+++ b/src/main/java/au/id/zancanaro/javacheck/Generators.java
@@ -179,6 +179,17 @@ public final class Generators {
         };
     }
 
+    public static <T> Generator<Set<T>> setOf(Generator<T> gen) {
+        return (random, size) -> {
+            Generator<Integer> countGen = sized(s -> integer(0, s));
+            int count = countGen.generate(random, size).getValue();
+            return Generator.list(count, gen)
+                    .generate(random, size)
+                    .map(HashSet::new)
+                    .map(Collections::unmodifiableSet);
+        };
+    }
+
     @SuppressWarnings("unchecked")
     public static <K, V> Generator<Map<K, V>> mapOf(Generator<K> keyGen, Generator<V> valueGen) {
         return (random, size) -> {
diff --git a/src/main/java/au/id/zancanaro/javacheck/object/GeneratorProvider.java b/src/main/java/au/id/zancanaro/javacheck/object/GeneratorProvider.java
index 827ba3f..c975933 100644
--- a/src/main/java/au/id/zancanaro/javacheck/object/GeneratorProvider.java
+++ b/src/main/java/au/id/zancanaro/javacheck/object/GeneratorProvider.java
@@ -11,6 +11,7 @@ import java.lang.reflect.TypeVariable;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 
 import static au.id.zancanaro.javacheck.Generators.*;
 
@@ -81,6 +82,11 @@ public interface GeneratorProvider {
                         List.class.getTypeParameters()[0],
                         new Annotation[0],
                         provider));
+            } else if (type == Set.class) {
+                return setOf(provider.getGenerator(
+                        Set.class.getTypeParameters()[0],
+                        new Annotation[0],
+                        provider));
             } else if (type == Map.class) {
                 TypeVariable<?>[] params = Map.class.getTypeParameters();
                 TypeVariable<?> keyType = params[0], valueType = params[1];
diff --git a/src/test/java/au/id/zancanaro/javacheck/CollectionsTest.java b/src/test/java/au/id/zancanaro/javacheck/CollectionsTest.java
new file mode 100644
index 0000000..644e8a1
--- /dev/null
+++ b/src/test/java/au/id/zancanaro/javacheck/CollectionsTest.java
@@ -0,0 +1,23 @@
+package au.id.zancanaro.javacheck;
+
+import au.id.zancanaro.javacheck.annotations.Property;
+import au.id.zancanaro.javacheck.junit.Properties;
+import org.junit.runner.RunWith;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static java.util.Collections.reverse;
+import static org.junit.Assert.assertEquals;
+
+@RunWith(Properties.class)
+public class CollectionsTest {
+    @Property
+    public void reverseIsInvolution(List<Integer> list) {
+        List<Integer> newList = new ArrayList<>(list);
+        reverse(newList);
+        reverse(newList);
+
+        assertEquals(list, newList);
+    }
+}
diff --git a/src/test/java/au/id/zancanaro/javacheck/OptionalFunctorRulesTest.java b/src/test/java/au/id/zancanaro/javacheck/OptionalRulesTest.java
index 5ef552e..407ffbd 100644
--- a/src/test/java/au/id/zancanaro/javacheck/OptionalFunctorRulesTest.java
+++ b/src/test/java/au/id/zancanaro/javacheck/OptionalRulesTest.java
@@ -14,7 +14,7 @@ import static au.id.zancanaro.javacheck.Generators.oneOf;
 import static org.junit.Assert.assertEquals;
 
 @RunWith(Properties.class)
-public class OptionalFunctorRulesTest {
+public class OptionalRulesTest {
 
     @DataSource
     public static Generator<Optional<Integer>> listOfIntegers = oneOf(
@@ -24,32 +24,23 @@ public class OptionalFunctorRulesTest {
     @DataSource
     public static Generator<Function<Integer, Integer>> integerFunction =
             oneOf(
-                    integer().map(OptionalFunctorRulesTest::plusI),
-                    integer().map(OptionalFunctorRulesTest::timesI),
-                    integer().map(OptionalFunctorRulesTest::constantlyI));
+                    integer().map(OptionalRulesTest::plusI),
+                    integer().map(OptionalRulesTest::timesI),
+                    integer().map(OptionalRulesTest::constantlyI));
 
     @Property
-    public void mappingCompositionsWithStreams(
-            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);
+    public void flatMapIdentity(Optional<Integer> optional) {
+        assertEquals(optional, optional.flatMap(Optional::of));
     }
 
     @Property
-    public void mappingCompositionsWithIntermediateList(
+    public void mappingComposition(
             Optional<Integer> optional,
             Function<Integer, Integer> f,
             Function<Integer, Integer> g) {
-        Optional<Integer> intermediate = optional.map(g);
-        Optional<Integer> left = intermediate.map(f);
+        Optional<Integer> left = optional
+                .map(g)
+                .map(f);
 
         Optional<Integer> right = optional
                 .map(x -> f.apply(g.apply(x)));
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;
+            }
+        };
+    }
+}
diff --git a/src/test/java/au/id/zancanaro/javacheck/SimpleListOperationsTest.java b/src/test/java/au/id/zancanaro/javacheck/SimpleListOperationsTest.java
index 3cfef37..93a40e2 100644
--- a/src/test/java/au/id/zancanaro/javacheck/SimpleListOperationsTest.java
+++ b/src/test/java/au/id/zancanaro/javacheck/SimpleListOperationsTest.java
@@ -27,11 +27,11 @@ public class SimpleListOperationsTest {
     }
 
     @Property
-    public void reverseIsItsOwnInverse(List<String> list) {
-        List<String> reversed = new ArrayList<>(list);
-        reverse(reversed);
-        reverse(reversed);
+    public void reverseIsInvolution(List<String> list) {
+        List<String> newList = new ArrayList<>(list);
+        reverse(newList);
+        reverse(newList);
 
-        assertEquals(list, reversed);
+        assertEquals(list, newList);
     }
 }