Add integration tests against a gqlgen server (#50)

## Summary:
We have lots of tests covering codegen, but not a lot that actually run
the code.  For things where all we do is generate types, that's (mostly)
fine (especially now that we actually build the code), but as we
generate more nontrivial non-type code we need to actually run it.

So I wrote some integration tests that spin up a little gqlgen
server, and make calls to it; we can add more over time especially as
the JSON marshalling logic gets complex (to support fragments).
They're more work to write than the snapshot tests, but of course they
can test a lot more.

In addition to gqlgen, I pulled in testify assert/require, because I
really wanted to be able to use assert.Equal and such for these.  I
didn't bother converting existing tests, although I assume they will
become useful elsewhere in time.  Both gqlgen and testify are of course
only used in tests.

Fixes #21 and #24.
Issue: #21
Issue: #24

## Test plan:
make check

Author: benjaminjkraft

Reviewers: aberkan, dnerdy, benjaminjkraft, csilvers, MiguelCastillo

Required Reviewers: 

Approved by: aberkan, dnerdy

Checks: ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14), ✅ Test (1.13), ✅ Lint, ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14), ✅ Test (1.13), ✅ Lint

Pull request URL: #50

.golangci.yml

@@ -69,6 +69,7 @@ linters-settings:
       - unnamedResult
       - ifElseChain
       - sloppyReassign
+      - typeDefFirst
 
     settings: # settings passed to gocritic
       captLocal: # must be valid enabled check name
@@ -80,7 +81,7 @@ issues:
     # Test-only deps are not restricted.
     - linters:
         - depguard
-      path: _test\.go$|internal/testutil/
+      path: _test\.go$|internal/testutil/|internal/integration/
 
     - linters:
         - errcheck

README.md

@@ -82,7 +82,12 @@ Khan Academy is a non-profit organization with a mission to provide a free, worl
 
 ### Tests
 
-To run tests and lint, `make check`.  (GitHub Actions also runs them.)  Most of the tests are snapshot-based; see `generate/generate_test.go`.  If `GITHUB_TOKEN` is available in the environment, it also checks that the example returns the expected output when run against the real API.  This is configured automatically in GitHub Actions, but you can also use a [personal access token](https://docs.github.com/en/github/authenticating-to-github/creating-a-personal-access-token) with no scopes.
+To run tests and lint, `make check`.  (GitHub Actions also runs them.)
+
+Notes for contributors:
+- Most of the tests are snapshot-based; see `generate/generate_test.go`.  All new code-generation logic should be snapshot-tested.  Some code additionally has standalone unit tests, when convenient.
+- Integration tests run against a gqlgen server in `internal/integration/integration_test.go`, and should cover everything that snapshot tests can't, including the GraphQL client code and JSON marshaling.
+- If `GITHUB_TOKEN` is available in the environment, it also checks that the example returns the expected output when run against the real API.  This is configured automatically in GitHub Actions, but you can also use a [personal access token](https://docs.github.com/en/github/authenticating-to-github/creating-a-personal-access-token) with no scopes.  There's no need for this to cover anything in particular; it's just to make sure the example in fact works.
 
 ### Design
 

example/genqlient.yaml

@@ -1,11 +1,11 @@
 # These are the defaults, and are just included to be explicit.
 package: example
 schema: schema.graphql
-queries:
+operations:
 - genqlient.graphql
 generated: generated.go
 
 # We map github's DateTime type to Go's time.Time (which conveniently already
-# defines MarshalJSON and UnmarshalJSAON).
+# defines MarshalJSON and UnmarshalJSON).
 scalars:
   DateTime: time.Time

generate/example_test.go

@@ -1,50 +1,16 @@
-package generate
+package generate_test
 
 import (
-	"bytes"
-	"io/ioutil"
 	"os"
 	"os/exec"
-	"path/filepath"
-	"runtime"
 	"strings"
 	"testing"
-)
-
-func getRepoRoot(t *testing.T) string {
-	_, thisFile, _, ok := runtime.Caller(0)
-	if !ok {
-		t.Fatal("runtime.Caller non-ok")
-	}
 
-	return filepath.Dir(filepath.Dir(thisFile))
-}
+	"github.com/Khan/genqlient/internal/integration"
+)
 
 func TestGenerateExample(t *testing.T) {
-	configFilename := filepath.Join(getRepoRoot(t), "example", "genqlient.yaml")
-	config, err := ReadAndValidateConfig(configFilename)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	generated, err := Generate(config)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	for filename, content := range generated {
-		expectedContent, err := ioutil.ReadFile(filename)
-		if err != nil {
-			t.Fatal(err)
-		}
-
-		if !bytes.Equal(content, expectedContent) {
-			t.Errorf("mismatch in %s", filename)
-			if testing.Verbose() {
-				t.Errorf("got:\n%s\nwant:\n%s\n", content, expectedContent)
-			}
-		}
-	}
+	integration.RunGenerateTest(t, "example/genqlient.yaml")
 }
 
 func TestRunExample(t *testing.T) {
@@ -53,7 +19,7 @@ func TestRunExample(t *testing.T) {
 	}
 
 	cmd := exec.Command("go", "run", "./example/cmd/example", "benjaminjkraft")
-	cmd.Dir = getRepoRoot(t)
+	cmd.Dir = integration.RepoRoot(t)
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		t.Error(err)

go.mod

@@ -3,9 +3,11 @@ module github.com/Khan/genqlient
 go 1.13
 
 require (
+	github.com/99designs/gqlgen v0.13.0
 	github.com/bradleyjkemp/cupaloy/v2 v2.6.0
 	// Should match golangci-lint version in .github/workflows/go.yml
 	github.com/golangci/golangci-lint v1.42.0
+	github.com/stretchr/testify v1.7.0
 	github.com/vektah/gqlparser/v2 v2.1.0
 	golang.org/x/tools v0.1.5
 	gopkg.in/yaml.v2 v2.4.0

internal/integration/genqlient.yaml

@@ -0,0 +1,4 @@
+schema: schema.graphql
+operations:
+- "*_test.go"
+generated: generated.go

internal/integration/integration_test.go

@@ -0,0 +1,66 @@
+// Package integration contains genqlient's integration tests, which run
+// against a real server (defined in internal/integration/server/server.go).
+//
+// These are especially important for cases where we generate nontrivial logic,
+// such as JSON-unmarshaling.
+package integration
+
+import (
+	"context"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/Khan/genqlient/graphql"
+	"github.com/Khan/genqlient/internal/integration/server"
+)
+
+func TestSimpleQuery(t *testing.T) {
+	_ = `# @genqlient
+	query simpleQuery { me { id name luckyNumber } }`
+
+	ctx := context.Background()
+	server := server.RunServer()
+	defer server.Close()
+	client := graphql.NewClient(server.URL, http.DefaultClient)
+
+	resp, err := simpleQuery(ctx, client)
+	require.NoError(t, err)
+
+	assert.Equal(t, "1", resp.Me.Id)
+	assert.Equal(t, "Yours Truly", resp.Me.Name)
+	assert.Equal(t, 17, resp.Me.LuckyNumber)
+}
+
+func TestVariables(t *testing.T) {
+	_ = `# @genqlient
+	query queryWithVariables($id: ID!) { user(id: $id) { id name luckyNumber } }`
+
+	ctx := context.Background()
+	server := server.RunServer()
+	defer server.Close()
+	client := graphql.NewClient(server.URL, http.DefaultClient)
+
+	resp, err := queryWithVariables(ctx, client, "2")
+	require.NoError(t, err)
+
+	assert.Equal(t, "2", resp.User.Id)
+	assert.Equal(t, "Raven", resp.User.Name)
+	assert.Equal(t, -1, resp.User.LuckyNumber)
+
+	resp, err = queryWithVariables(ctx, client, "374892379482379")
+	require.NoError(t, err)
+
+	assert.Zero(t, resp.User)
+}
+
+func TestGeneratedCode(t *testing.T) {
+	// TODO(benkraft): Check that gqlgen is up to date too.  In practice that's
+	// less likely to be a problem, since it should only change if you update
+	// the schema, likely too add something new, in which case you'll notice.
+	RunGenerateTest(t, "internal/integration/genqlient.yaml")
+}
+
+//go:generate go run github.com/Khan/genqlient genqlient.yaml

internal/integration/schema.graphql

@@ -0,0 +1,10 @@
+type Query {
+  me: User
+  user(id: ID!): User
+}
+
+type User {
+  id: ID!
+  name: String!
+  luckyNumber: Int
+}

internal/integration/server/gqlgen.yml

@@ -0,0 +1,10 @@
+schema:
+- ../schema.graphql
+
+exec:
+  filename: gqlgen_exec.go
+  package: server
+
+model: 
+  filename: gqlgen_models.go
+  package: server