diff --git a/act/artifactcache/mac_test.go b/act/artifactcache/mac_test.go
new file mode 100644
index 00000000..10d6c5a8
--- /dev/null
+++ b/act/artifactcache/mac_test.go
@@ -0,0 +1,80 @@
+package artifactcache
+
+import (
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/nektos/act/pkg/cacheproxy"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMac(t *testing.T) {
+	handler := &Handler{
+		secret: "secret for testing",
+	}
+
+	t.Run("validate correct mac", func(t *testing.T) {
+		name := "org/reponame"
+		run := "1"
+		ts := strconv.FormatInt(time.Now().Unix(), 10)
+
+		mac := computeMac(handler.secret, name, run, ts)
+		rundata := cacheproxy.RunData{
+			RepositoryFullName: name,
+			RunNumber:          run,
+			Timestamp:          ts,
+			RepositoryMAC:      mac,
+		}
+
+		repoName, err := handler.validateMac(rundata)
+		require.NoError(t, err)
+		require.Equal(t, name, repoName)
+	})
+
+	t.Run("validate incorrect timestamp", func(t *testing.T) {
+		name := "org/reponame"
+		run := "1"
+		ts := "9223372036854775807" // This should last us for a while...
+
+		mac := computeMac(handler.secret, name, run, ts)
+		rundata := cacheproxy.RunData{
+			RepositoryFullName: name,
+			RunNumber:          run,
+			Timestamp:          ts,
+			RepositoryMAC:      mac,
+		}
+
+		_, err := handler.validateMac(rundata)
+		require.Error(t, err)
+	})
+
+	t.Run("validate incorrect mac", func(t *testing.T) {
+		name := "org/reponame"
+		run := "1"
+		ts := strconv.FormatInt(time.Now().Unix(), 10)
+
+		rundata := cacheproxy.RunData{
+			RepositoryFullName: name,
+			RunNumber:          run,
+			Timestamp:          ts,
+			RepositoryMAC:      "this is not the right mac :D",
+		}
+
+		repoName, err := handler.validateMac(rundata)
+		require.Error(t, err)
+		require.Equal(t, name, repoName)
+	})
+
+	t.Run("compute correct mac", func(t *testing.T) {
+		secret := "this is my cool secret string :3"
+		name := "org/reponame"
+		run := "42"
+		ts := "1337"
+
+		mac := computeMac(secret, name, run, ts)
+		expectedMac := "09b0e9111660359d319c2d55c0664b5a6c5915c2f705b08af61aa63e7542f511" // * Precomputed, anytime the computeMac function changes this needs to be recalculated
+
+		require.Equal(t, mac, expectedMac)
+	})
+}