terraform: acceptance test for validation error

Add an acceptance test where terraform plan should error due
to validation errors.

terraform/context_test.go

@@ -4148,6 +4148,22 @@ func TestContextPlan_varMultiCountOne(t *testing.T) {
 	}
 }
 
+func TestContextPlan_varListErr(t *testing.T) {
+	m := testModule(t, "plan-var-list-err")
+	p := testProvider("aws")
+	ctx := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	_, err := ctx.Plan(nil)
+	if err == nil {
+		t.Fatal("should error")
+	}
+}
+
 func TestContextRefresh(t *testing.T) {
 	p := testProvider("aws")
 	m := testModule(t, "refresh-basic")

terraform/test-fixtures/plan-var-list-err/main.tf

@@ -0,0 +1,16 @@
+provider "aws" {
+    access_key = "a"
+    secret_key = "b"
+    region = "us-east-1"
+}
+
+resource "aws_instance" "foo" {
+    ami = "ami-foo"
+    instance_type = "t2.micro"
+    security_groups = "${aws_security_group.foo.name}"
+}
+
+resource "aws_security_group" "foo" {
+    name = "foobar"
+    description = "foobar"
+}