add unit test

test/BUILD

@@ -18,7 +18,7 @@ go_binary(
 )
 
 go_test(
-    name = "test_test",
+    name = "hello_test",
     srcs = ["hello_test.go"],
-    embed = [":test_lib"],
+    embed = [":hello_lib"],
 )

test/hello.go

@@ -5,8 +5,8 @@ import (
 )
 
 // #include <stdio.h>
-// char* hello() { return "hello, world\n"; }
-// void printhello() { printf(hello()); }
+// char* hello() { return "hello, world"; }
+// void printhello() { printf("%s\n", hello()); }
 import "C"
 
 func main() {

test/hello_test.go

@@ -0,0 +1,11 @@
+package main
+
+import "testing"
+
+func TestHello(t *testing.T) {
+	want := "hello, world"
+	got := chello()
+	if got != want {
+		t.Errorf("expected %q, got %q", want, got)
+	}
+}