config: validate good count variables

config/config_test.go

@@ -95,6 +95,13 @@ func TestConfigValidate_countUserVar(t *testing.T) {
 	}
 }
 
+func TestConfigValidate_countVar(t *testing.T) {
+	c := testConfig(t, "validate-count-var")
+	if err := c.Validate(); err != nil {
+		t.Fatal("err: %s", err)
+	}
+}
+
 func TestConfigValidate_countVarInvalid(t *testing.T) {
 	c := testConfig(t, "validate-count-var-invalid")
 	if err := c.Validate(); err == nil {

config/test-fixtures/validate-count-var/main.tf

@@ -0,0 +1,3 @@
+resource "aws_instance" "foo" {
+    foo = "${count.index}"
+}