diff --git a/lib/common_test.go b/lib/common_test.go
new file mode 100644
index 0000000..43371aa
--- /dev/null
+++ b/lib/common_test.go
@@ -0,0 +1,28 @@
+package lib
+
+import "testing"
+
+func TestHasCommand(t *testing.T) {
+	tables := []struct {
+		s      string
+		prefix string
+		cmd    string
+		r      bool
+	}{
+		{"!command x y", "!", "command", true},
+		{"#command x y", "#", "command", true},
+		{"command x y", "!", "comamnd", false},
+		{"", "", "", false},
+		{"!", "!", "", false},
+		{"! x y", "!", "", false},
+	}
+
+	for _, table := range tables {
+		r := HasCommand(table.s, table.prefix, table.cmd)
+		if r != table.r {
+			t.Errorf("HasCommand(%q, %q, %q), got: %t, want: %t",
+				table.s, table.prefix, table.cmd, r, table.r,
+			)
+		}
+	}
+}