feat(render): experimental package to render arbitrary values to different formats

writer_to_test.go

@@ -0,0 +1,84 @@
+package render_test
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"testing"
+
+	"github.com/jimeh/go-render"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type mockWriterTo struct {
+	value string
+	err   error
+}
+
+func (m *mockWriterTo) WriteTo(w io.Writer) (int64, error) {
+	n, err := w.Write([]byte(m.value))
+
+	if m.err != nil {
+		return int64(n), m.err
+	}
+
+	return int64(n), err
+}
+
+func TestWriterTo_Render(t *testing.T) {
+	tests := []struct {
+		name      string
+		writeErr  error
+		value     any
+		want      string
+		wantErr   string
+		wantErrIs []error
+	}{
+		{
+			name:  "implements io.WriterTo",
+			value: &mockWriterTo{value: "test string"},
+			want:  "test string",
+		},
+		{
+			name:      "does not implement io.WriterTo",
+			value:     struct{}{},
+			wantErr:   "render: cannot render",
+			wantErrIs: []error{render.Err, render.ErrCannotRender},
+		},
+		{
+			name: "error writing to writer",
+			value: &mockWriterTo{
+				value: "test string",
+				err:   errors.New("WriteTo error!!1"),
+			},
+			wantErr:   "render: WriteTo error!!1",
+			wantErrIs: []error{render.Err},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			wt := &render.WriterTo{}
+
+			var err error
+			var got string
+			w := &bytes.Buffer{}
+
+			err = wt.Render(w, tt.value)
+			got = w.String()
+
+			if tt.wantErr != "" {
+				require.Error(t, err)
+				assert.EqualError(t, err, tt.wantErr)
+			}
+			for _, e := range tt.wantErrIs {
+				assert.ErrorIs(t, err, e)
+			}
+
+			if tt.wantErr == "" && len(tt.wantErrIs) == 0 {
+				require.NoError(t, err)
+				assert.Equal(t, tt.want, got)
+			}
+		})
+	}
+}