diff --git a/.gitignore b/.gitignore
index 4eb156d..4884a41 100644
--- a/.gitignore
+++ b/.gitignore
@@ -20,4 +20,5 @@ _cgo_export.*
 _testmain.go
 
 *.exe
-.idea
\ No newline at end of file
+.idea
+coverage.txt
\ No newline at end of file
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..501caa3
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,12 @@
+SOURCE_FILES?=./...
+TEST_PATTERN?=.
+
+export GO111MODULE := on
+
+test:
+	go test -v -failfast -race -coverpkg=./... -covermode=atomic -coverprofile=coverage.txt $(SOURCE_FILES) -run $(TEST_PATTERN) -timeout=2m
+.PHONY: test
+
+cover: test
+	go tool cover -html=coverage.txt
+.PHONY: cover
\ No newline at end of file
diff --git a/set_test.go b/set_test.go
index 7c5f611..70c79a9 100644
--- a/set_test.go
+++ b/set_test.go
@@ -26,6 +26,7 @@ SOFTWARE.
 package mapset
 
 import (
+	"strings"
 	"testing"
 )
 
@@ -76,6 +77,19 @@ func Test_NewSet(t *testing.T) {
 	assertEqual(NewSet([]string{"a", "b"}...), NewSet("a", "b"), t)
 }
 
+func Test_newThreadSafeSet(t *testing.T) {
+	a := newThreadSafeSet[int]()
+	if a.Cardinality() != 0 {
+		t.Error("NewSet should start out as an empty set")
+	}
+
+	assertEqual(NewSet([]int{}...), NewSet[int](), t)
+	assertEqual(NewSet([]int{1}...), NewSet(1), t)
+	assertEqual(NewSet([]int{1, 2}...), NewSet(1, 2), t)
+	assertEqual(NewSet([]string{"a"}...), NewSet("a"), t)
+	assertEqual(NewSet([]string{"a", "b"}...), NewSet("a", "b"), t)
+}
+
 func Test_NewUnsafeSet(t *testing.T) {
 	a := NewThreadUnsafeSet[int]()
 
@@ -424,7 +438,12 @@ func Test_ContainsAnyElement(t *testing.T) {
 	if ret := a.ContainsAnyElement(b); !ret {
 		t.Errorf("set a contain 10")
 	}
+
+	if ret := b.ContainsAnyElement(a); !ret {
+		t.Errorf("set a contain 10")
+	}
 }
+
 func Test_ClearSet(t *testing.T) {
 	a := makeSetInt([]int{2, 5, 9, 10})
 
@@ -526,6 +545,10 @@ func Test_SetIsSubset(t *testing.T) {
 	if b.IsSubset(a) {
 		t.Error("set b should not be a subset of set a because it contains 72 which is not in the set of a")
 	}
+
+	if a.IsSubset(b) {
+		t.Error("set b should not be a subset of set a because it contains 72 which is not in the set of a")
+	}
 }
 
 func Test_SetIsProperSubset(t *testing.T) {
@@ -805,6 +828,12 @@ func Test_SetIntersect(t *testing.T) {
 		t.Error("set c should be the empty set because there is no common items to intersect")
 	}
 
+	c = b.Intersect(a)
+
+	if c.Cardinality() != 0 {
+		t.Error("set c should be the empty set because there is no common items to intersect")
+	}
+
 	a.Add(10)
 	b.Add(10)
 
@@ -813,6 +842,12 @@ func Test_SetIntersect(t *testing.T) {
 	if !(d.Cardinality() == 1 && d.Contains(10)) {
 		t.Error("set d should have a size of 1 and contain the item 10")
 	}
+
+	d = b.Intersect(a)
+
+	if !(d.Cardinality() == 1 && d.Contains(10)) {
+		t.Error("set d should have a size of 1 and contain the item 10")
+	}
 }
 
 func Test_UnsafeSetIntersect(t *testing.T) {
@@ -832,6 +867,12 @@ func Test_UnsafeSetIntersect(t *testing.T) {
 		t.Error("set c should be the empty set because there is no common items to intersect")
 	}
 
+	c = b.Intersect(a)
+
+	if c.Cardinality() != 0 {
+		t.Error("set c should be the empty set because there is no common items to intersect")
+	}
+
 	a.Add(10)
 	b.Add(10)
 
@@ -840,6 +881,12 @@ func Test_UnsafeSetIntersect(t *testing.T) {
 	if !(d.Cardinality() == 1 && d.Contains(10)) {
 		t.Error("set d should have a size of 1 and contain the item 10")
 	}
+
+	d = b.Intersect(a)
+
+	if !(d.Cardinality() == 1 && d.Contains(10)) {
+		t.Error("set d should have a size of 1 and contain the item 10")
+	}
 }
 
 func Test_SetDifference(t *testing.T) {
@@ -963,6 +1010,12 @@ func Test_SetEqual(t *testing.T) {
 	if !a.Equal(b) {
 		t.Error("a and b should be equal with the same number of elements")
 	}
+
+	a.Add(12)
+	b.Add(22)
+	if a.Equal(b) {
+		t.Error("a and b have different elements and should not be equal")
+	}
 }
 
 func Test_UnsafeSetEqual(t *testing.T) {
@@ -1081,6 +1134,37 @@ func Test_Each(t *testing.T) {
 	}
 }
 
+func Test_UnSafeEach(t *testing.T) {
+	a := NewThreadUnsafeSet[string]()
+
+	a.Add("Z")
+	a.Add("Y")
+	a.Add("X")
+	a.Add("W")
+
+	b := NewThreadUnsafeSet[string]()
+	a.Each(func(elem string) bool {
+		b.Add(elem)
+		return false
+	})
+
+	if !a.Equal(b) {
+		t.Error("The sets are not equal after iterating (Each) through the first set")
+	}
+
+	var count int
+	a.Each(func(elem string) bool {
+		if count == 2 {
+			return true
+		}
+		count++
+		return false
+	})
+	if count != 2 {
+		t.Error("Iteration should stop on the way")
+	}
+}
+
 func Test_Iter(t *testing.T) {
 	a := NewSet[string]()
 
@@ -1168,6 +1252,21 @@ func Test_IteratorStop(t *testing.T) {
 	}
 }
 
+func Test_UnsafeIteratorStop(t *testing.T) {
+	a := NewThreadUnsafeSet[string]()
+
+	a.Add("Z")
+	a.Add("Y")
+	a.Add("X")
+	a.Add("W")
+
+	it := a.Iterator()
+	it.Stop()
+	for range it.C {
+		t.Error("The iterating (Iterator) did not stop after Stop() has been called")
+	}
+}
+
 func Test_PopSafe(t *testing.T) {
 	a := NewSet[string]()
 
@@ -1297,6 +1396,20 @@ func Test_ToSliceUnthreadsafe(t *testing.T) {
 	}
 }
 
+func Test_ToSliceThreadSafe(t *testing.T) {
+	s := makeSetInt([]int{1, 2, 3})
+	setAsSlice := s.ToSlice()
+	if len(setAsSlice) != s.Cardinality() {
+		t.Errorf("Set length is incorrect: %v", len(setAsSlice))
+	}
+
+	for _, i := range setAsSlice {
+		if !s.Contains(i) {
+			t.Errorf("Set is missing element: %v", i)
+		}
+	}
+}
+
 func Test_NewSetFromMapKey_Ints(t *testing.T) {
 	m := map[int]int{
 		5: 5,
@@ -1373,6 +1486,66 @@ func Test_NewThreadUnsafeSetFromMapKey_Strings(t *testing.T) {
 	}
 }
 
+func Test_StringSafe(t *testing.T) {
+	strSlice := []string{"a", "b", "c", "d"}
+	strSet := NewSet(strSlice...)
+
+	strSetToSlice := strSet.ToSlice()
+	strSetToString := strSet.String()
+	for _, v := range strSetToSlice {
+		if !strings.Contains(strSetToString, v) {
+			t.Errorf("String representation of set does not contain %s", v)
+		}
+	}
+}
+
+func Test_StringUnSafe(t *testing.T) {
+	strSlice := []string{"a", "b", "c", "d"}
+	strSet := NewThreadUnsafeSet(strSlice...)
+
+	strSetToSlice := strSet.ToSlice()
+	strSetToString := strSet.String()
+	for _, v := range strSetToSlice {
+		if !strings.Contains(strSetToString, v) {
+			t.Errorf("String representation of set does not contain %s", v)
+		}
+	}
+}
+
+func Test_IsEmptySafe(t *testing.T) {
+	s := NewSet[int]()
+	if !s.IsEmpty() {
+		t.Error("Set should be empty")
+	}
+
+	s.Add(1)
+	if s.IsEmpty() {
+		t.Error("Set should not be empty")
+	}
+
+	s.Remove(1)
+	if !s.IsEmpty() {
+		t.Error("Set should be empty")
+	}
+}
+
+func Test_IsEmptyUnSafe(t *testing.T) {
+	s := NewThreadUnsafeSet[int]()
+	if !s.IsEmpty() {
+		t.Error("Set should be empty")
+	}
+
+	s.Add(1)
+	if s.IsEmpty() {
+		t.Error("Set should not be empty")
+	}
+
+	s.Remove(1)
+	if !s.IsEmpty() {
+		t.Error("Set should be empty")
+	}
+}
+
 func Test_Example(t *testing.T) {
 	/*
 	   requiredClasses := NewSet()
diff --git a/threadsafe_test.go b/threadsafe_test.go
index 9037616..c2d4f9a 100644
--- a/threadsafe_test.go
+++ b/threadsafe_test.go
@@ -636,3 +636,21 @@ func Test_MarshalJSON(t *testing.T) {
 		t.Errorf("Expected no difference, got: %v", expected.Difference(actual))
 	}
 }
+
+func Test_MarshalJSONError(t *testing.T) {
+	a := NewSet([]complex128{1 + 2i, 2 + 2i}...)
+	_, err := a.MarshalJSON()
+	if err == nil {
+		t.Error("Error should not be nil")
+	}
+}
+
+func Test_UnmarshalJSONError(t *testing.T) {
+	a := NewThreadUnsafeSet[int64]()
+
+	err := a.UnmarshalJSON([]byte(`[s, 2, 3]`))
+	if err == nil {
+		t.Error("Error should not be nil")
+	}
+
+}