// packages by name (if nil, then all packages are included).
func MakeCovDataReader(vis CovDataVisitor, indirs []string, verbosityLevel int, flags CovDataReaderFlags, matchpkg func(name string) bool) *CovDataReader {
	return &CovDataReader{
		vis:            vis,
		indirs:         indirs,
		matchpkg:       matchpkg,
		verbosityLevel: verbosityLevel,
		flags:          flags,
	}
}

// CovDataVisitor defines hooks for clients of CovDataReader. When the

		t.Fatalf("build error: %v", err)
	}

	vis := &visitor{}

	// Read resulting coverage data. Without the fix, this would
	// yield a "short read" error.
	const verbosityLevel = 0
	const flags = 0
	cdr := cov.MakeCovDataReader(vis, []string{covdir}, verbosityLevel, flags, nil)
	err = cdr.Visit()
	if err != nil {
		t.Fatalf("visit failed: %v", err)
	}

	// make sure we saw a few things just for grins