move everything into snapshot-based testing; update it a bit

generate/generate_test.go

@@ -0,0 +1,85 @@
+package generate
+
+import (
+	"errors"
+	"fmt"
+	"go/format"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+const dataDir = "testdata"
+
+func readFile(t *testing.T, filename string, allowNotExist bool) string {
+	t.Helper()
+	data, err := ioutil.ReadFile(filepath.Join(dataDir, filename))
+	if err != nil {
+		if allowNotExist && errors.Is(err, os.ErrNotExist) {
+			return ""
+		}
+		t.Fatal(err)
+	}
+	return string(data)
+}
+
+func gofmt(src string) (string, error) {
+	src = strings.TrimSpace(src)
+	formatted, err := format.Source([]byte(src))
+	if err != nil {
+		return src, fmt.Errorf("go parse error: %w", err)
+	}
+	return string(formatted), nil
+}
+
+func TestGenerate(t *testing.T) {
+	// This test uses the schema, queries, and expected-output in ./testdata.
+	// The schema is in schema.graphql.  The queries are in TestName.graphql;
+	// the test asserts that the output of the generator for that query is
+	// matches TestName.graphql.go.  To update the expected output, run the
+	// tests with UPDATE_SNAPSHOTS=1 (they will still fail, but also do the
+	// update, so you can see which updates were made).
+	update := (os.Getenv("UPDATE_SNAPSHOTS") == "1")
+
+	files, err := ioutil.ReadDir(dataDir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, file := range files {
+		graphqlFilename := file.Name()
+		if graphqlFilename == "schema.graphql" || !strings.HasSuffix(graphqlFilename, ".graphql") {
+			continue
+		}
+		goFilename := graphqlFilename + ".go"
+
+		t.Run(graphqlFilename, func(t *testing.T) {
+			expectedGoCode, err := gofmt(readFile(t, goFilename, update))
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			goCode, err := Generate(&Config{
+				Schema:  filepath.Join("testdata", "schema.graphql"),
+				Queries: filepath.Join("testdata", graphqlFilename),
+				Package: "test",
+			})
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if string(goCode) != expectedGoCode {
+				t.Errorf("got:\n%v\nwant:\n%v\n", string(goCode), expectedGoCode)
+				if update {
+					t.Log("Updating testdata dir to match")
+					err = ioutil.WriteFile(filepath.Join(dataDir, goFilename), goCode, 0644)
+					if err != nil {
+						t.Errorf("Unable to update testdata dir: %v", err)
+					}
+				}
+			}
+		})
+	}
+}