diff --git a/.github/workflows/llgo.yml b/.github/workflows/llgo.yml
index 08fe6249..50756e0e 100644
--- a/.github/workflows/llgo.yml
+++ b/.github/workflows/llgo.yml
@@ -165,6 +165,7 @@ jobs:
 
       - name: run llgo test
         run: |
+          llgo test ./...
           cd _demo
           llgo test -v ./runtest
 
diff --git a/test/c_test.go b/test/c_test.go
new file mode 100644
index 00000000..4802d6d1
--- /dev/null
+++ b/test/c_test.go
@@ -0,0 +1,21 @@
+//go:build llgo
+// +build llgo
+
+package test
+
+import (
+	"testing"
+
+	"github.com/goplus/llgo/c"
+)
+
+// Can't put it in c/ package because it is marked as 'decl'
+func TestCstr(t *testing.T) {
+	cstr := c.Str("foo")
+	if cstr == nil {
+		t.Fatal("cstr() returned nil")
+	}
+	if c.Strlen(cstr) != 3 {
+		t.Fatal("cstr() returned invalid length")
+	}
+}