diff --git a/README.md b/README.md
index 9460f5b..46d44ea 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # mcache
 
-`mcache` is a simple and thread-safe in-memory cache library for Go.
+`mcache` is a simple, fast, thread-safe in-memory cache library with by-key TTL written in Go.
 
 ## Features
 
@@ -144,9 +144,19 @@ go func() {
 
 See the [examples](https://github.com/parMaster/mcache/tree/main/examples) directory for more examples.
 
-## Benchmarks
+## Tests and Benchmarks
+
+100% test coverage:
+
+```shell
+$ go test -race .
+
+ok      github.com/parMaster/mcache     8.239s  coverage: 100.0% of statements
+```
+Blinding fast and efficient:
+
 ```shell
-Running tool: /usr/local/go/bin/go test -benchmem -run=^$ -coverprofile=/tmp/vscode-gopk5hiw/go-code-cover -bench . github.com/parMaster/mcache
+$ go test -bench . -benchmem
 
 goos: linux
 goarch: amd64
diff --git a/main_test.go b/main_test.go
index eb824e2..26ddf83 100644
--- a/main_test.go
+++ b/main_test.go
@@ -74,7 +74,36 @@ func Test_SimpleTest_Mcache(t *testing.T) {
 		assert.Equal(t, ErrKeyNotFound, err.Error())
 	}
 
+	c.Set("key", "value", 1)
+	time.Sleep(time.Second * 2)
+	err = c.Set("key", "newvalue", 1)
+	assert.NoError(t, err)
+
+	// old value should be rewritten
+	value, err := c.Get("key")
+	assert.NoError(t, err)
+	assert.Equal(t, "newvalue", value)
+
+	err = c.Set("key", "not a newer value", 1)
+	assert.Equal(t, ErrKeyExists, err.Error())
+
+	time.Sleep(time.Second * 2)
+	err = c.Set("key", "even newer value", 1)
+	// key should be silently rewritten
+	assert.NoError(t, err)
+	value, err = c.Get("key")
+	assert.NoError(t, err)
+	assert.Equal(t, "even newer value", value)
+
+	time.Sleep(time.Second * 2)
 	c.Cleanup()
+	// key should be deleted
+	has, err = c.Has("key")
+	assert.False(t, has)
+
+	// del should return error if key doesn't exist
+	err = c.Del("noSuchKey")
+	assert.Error(t, err)
 
 	err = c.Clear()
 	assert.NoError(t, err)