dargs := []string{"-pkg=" + mainPkgPath, "-i=" + s.outdirs[0] + "," + s.outdirs[1],
		"-o", outf}
	lines := runToolOp(t, s, "textfmt", dargs)

	// No output expected.
	if len(lines) != 0 {
		dumplines(lines)
		t.Errorf("unexpected output from go tool covdata textfmt")
	}

	// Open and read the first few bits of the file.
	payload, err := os.ReadFile(outf)
	if err != nil {

}

func usage(msg string) {
	if len(msg) > 0 {
		fmt.Fprintf(os.Stderr, "error: %s\n", msg)
	}
	fmt.Fprintf(os.Stderr, "usage: go tool covdata [command]\n")
	fmt.Fprintf(os.Stderr, `
Commands are:

textfmt     convert coverage data to textual format
percent     output total percentage of statements covered
pkglist     output list of package import paths
func        output coverage profile information for each function

	}
}

const (
	// nolint: revive, stylecheck
	FmtOpenMetrics_0_0_1 = expfmt.OpenMetricsType + `; version=` + expfmt.OpenMetricsVersion_0_0_1 + `; charset=utf-8`
	// nolint: revive, stylecheck
	FmtOpenMetrics_1_0_0 = expfmt.OpenMetricsType + `; version=` + expfmt.OpenMetricsVersion_1_0_0 + `; charset=utf-8`
	FmtText              = `text/plain; version=` + expfmt.TextVersion + `; charset=utf-8`
)

				return
			}
		}

		contentType := expfmt.Negotiate(r.Header)
		w.Header().Set("Content-Type", string(contentType))

		enc := expfmt.NewEncoder(w, contentType)
		for _, mf := range mfs {
			if err := enc.Encode(mf); err != nil {
				// client may disconnect for any reasons
				// we do not have to log this.
				return
			}
		}
		if closer, ok := enc.(expfmt.Closer); ok {
			closer.Close()
		}
	})

		},
		{
			name:        "plaintext accept header",
			contentType: "text/plain; version=0.0.4; charset=utf-8",
			expected:    expfmt.NewFormat(expfmt.TypeTextPlain),
		},
		{
			name:        "empty accept header",
			contentType: "",
			expected:    expfmt.NewFormat(expfmt.TypeTextPlain),
		},
	}
	for _, tt := range cases {
		t.Run(tt.name, func(t *testing.T) {

			return
		}

		contentType := expfmt.Negotiate(r.Header)
		w.Header().Set("Content-Type", string(contentType))

		enc := expfmt.NewEncoder(w, contentType)
		for _, mf := range mfs {
			if err := enc.Encode(mf); err != nil {
				// client may disconnect for any reasons
				// we do not have to log this.
				return
			}
		}
		if closer, ok := enc.(expfmt.Closer); ok {
			closer.Close()
		}