Index: tests/OFArrayTests.m
==================================================================
--- tests/OFArrayTests.m
+++ tests/OFArrayTests.m
@@ -96,10 +96,28 @@
 	OFArray *array = [self.arrayClass arrayWithObjects: cArray count: 3];
 
 	OTAssertEqualObjects(array, _array);
 	OTAssertNotEqual(array, _array);
 }
+
+- (void)testHash
+{
+	OFArray *array = [self.arrayClass arrayWithObjects: cArray count: 3];
+
+	OTAssertEqual(array.hash, _array.hash);
+	OTAssertNotEqual(array.hash, [[OFArray array] hash]);
+}
+
+- (void)testCopy
+{
+	OTAssertEqualObjects([[_array copy] autorelease], _array);
+}
+
+- (void)testMutableCopy
+{
+	OTAssertEqualObjects([[_array mutableCopy] autorelease], _array);
+}
 
 - (void)testObjectAtIndex
 {
 	OTAssertEqualObjects([_array objectAtIndex: 0], cArray[0]);
 	OTAssertEqualObjects([_array objectAtIndex: 1], cArray[1]);

Index: tests/OFDictionaryTests.m
==================================================================
--- tests/OFDictionaryTests.m
+++ tests/OFDictionaryTests.m
@@ -90,10 +90,16 @@
 
 - (void)testCopy
 {
 	OTAssertEqualObjects([[_dictionary copy] autorelease], _dictionary);
 }
+
+- (void)testMutableCopy
+{
+	OTAssertEqualObjects(
+	    [[_dictionary mutableCopy] autorelease], _dictionary);
+}
 
 - (void)testValueForKey
 {
 	OTAssertEqualObjects([_dictionary valueForKey: keys[0]], objects[0]);
 	OTAssertEqualObjects([_dictionary valueForKey: keys[1]], objects[1]);

Index: tests/OFSetTests.m
==================================================================
--- tests/OFSetTests.m
+++ tests/OFSetTests.m
@@ -77,10 +77,15 @@
 
 - (void)testCopy
 {
 	OTAssertEqualObjects([[_set copy] autorelease], _set);
 }
+
+- (void)testMutableCopy
+{
+	OTAssertEqualObjects([[_set mutableCopy] autorelease], _set);
+}
 
 - (void)testIsSubsetOfSet
 {
 	OTAssertTrue([([OFSet setWithObjects: @"foo", nil])
 	    isSubsetOfSet: _set]);

Index: tests/OFStringTests.m
==================================================================
--- tests/OFStringTests.m
+++ tests/OFStringTests.m
@@ -89,10 +89,20 @@
 {
 	OTAssertEqual(_string.hash, @"täṠ€🤔".hash);
 	OTAssertNotEqual([[self.stringClass stringWithString: @"test"] hash],
 	    @"täṠ€".hash);
 }
+
+- (void)testCopy
+{
+	OTAssertEqualObjects([[_string copy] autorelease], _string);
+}
+
+- (void)testMutableCopy
+{
+	OTAssertEqualObjects([[_string mutableCopy] autorelease], _string);
+}
 
 - (void)testCompare
 {
 	OTAssertEqual([_string compare: @"täṠ€🤔"], OFOrderedSame);
 	OTAssertEqual([[self.stringClass stringWithString: @""]