refactor: add contextual stdio for better testing

cmd/yoke/cmd_blackbox.go

@@ -180,6 +180,6 @@ func Blackbox(ctx context.Context, params BlackboxParams) error {
 		return err
 	}
 
-	_, err = fmt.Fprint(os.Stdout, text.DiffColorized(a, b, params.Context))
+	_, err = fmt.Fprint(internal.Stdout(ctx), text.DiffColorized(a, b, params.Context))
 	return err
 }

cmd/yoke/cmd_takeoff.go

@@ -152,7 +152,7 @@ func TakeOff(ctx context.Context, params TakeoffParams) error {
 			return err
 		}
 
-		_, err = fmt.Fprint(os.Stdout, text.DiffColorized(a, b, params.Context))
+		_, err = fmt.Fprint(internal.Stdout(ctx), text.DiffColorized(a, b, params.Context))
 		return err
 	}
 

cmd/yoke/main_test.go

@@ -17,6 +17,7 @@ import (
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/tools/clientcmd"
 
+	"github.com/davidmdm/yoke/internal"
 	"github.com/davidmdm/yoke/internal/home"
 	"github.com/davidmdm/yoke/internal/k8s"
 )
@@ -229,7 +230,10 @@ func TestTurbulenceFix(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, "corrupt", configmap.Data["key"])
 
-	require.NoError(t, Turbulence(context.Background(), TurbulenceParams{GlobalSettings: settings, Release: "foo", Fix: true}))
+	var stderr bytes.Buffer
+	ctx := internal.WithStderr(context.Background(), &stderr)
+	require.NoError(t, Turbulence(ctx, TurbulenceParams{GlobalSettings: settings, Release: "foo", Fix: true}))
+	require.Equal(t, "fixed drift for: default.core.v1.configmap.test\n", stderr.String())
 
 	configmap, err = client.CoreV1().ConfigMaps("default").Get(context.Background(), "test", metav1.GetOptions{})
 	require.NoError(t, err)

internal/io.go

@@ -0,0 +1,49 @@
+package internal
+
+import (
+	"context"
+	"io"
+	"os"
+)
+
+type (
+	stdoutKey struct{}
+	stderrKey struct{}
+	stdinKey  struct{}
+)
+
+func WithStdout(ctx context.Context, w io.Writer) context.Context {
+	return context.WithValue(ctx, stdoutKey{}, w)
+}
+
+func Stdout(ctx context.Context) io.Writer {
+	w, ok := ctx.Value(stdoutKey{}).(io.Writer)
+	if !ok {
+		return os.Stdout
+	}
+	return w
+}
+
+func WithStderr(ctx context.Context, w io.Writer) context.Context {
+	return context.WithValue(ctx, stderrKey{}, w)
+}
+
+func Stderr(ctx context.Context) io.Writer {
+	w, ok := ctx.Value(stderrKey{}).(io.Writer)
+	if !ok {
+		return os.Stderr
+	}
+	return w
+}
+
+func WithStdin(ctx context.Context, r io.Reader) context.Context {
+	return context.WithValue(ctx, stdinKey{}, r)
+}
+
+func Stdin(ctx context.Context) io.Reader {
+	r, ok := ctx.Value(stdinKey{}).(io.Reader)
+	if !ok {
+		return os.Stdin
+	}
+	return r
+}

pkg/yoke/yoke.go

@@ -3,7 +3,6 @@ package yoke
 import (
 	"context"
 	"fmt"
-	"os"
 	"reflect"
 
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
@@ -214,7 +213,7 @@ func (client Client) Turbulence(ctx context.Context, params TurbulenceParams) er
 			if err := client.k8s.ApplyResource(ctx, desired, forceConflicts); err != nil {
 				errs = append(errs, fmt.Errorf("%s: %w", name, err))
 			}
-			fmt.Fprintf(os.Stderr, "fixed drift for: %s\n", name)
+			fmt.Fprintf(internal.Stderr(ctx), "fixed drift for: %s\n", name)
 		}
 
 		return xerr.MultiErrOrderedFrom("failed to apply desired state to drift", errs...)
@@ -243,7 +242,7 @@ func (client Client) Turbulence(ctx context.Context, params TurbulenceParams) er
 		return internal.Warning("no turbulence detected")
 	}
 
-	_, err = fmt.Fprint(os.Stdout, diff)
+	_, err = fmt.Fprint(internal.Stdout(ctx), diff)
 	return err
 }