go/src/testing/iotest/reader.go

// OneByteReader returns a Reader that implements
// each non-empty Read by reading one byte from r.
func OneByteReader(r io.Reader) io.Reader { … }

type oneByteReader …

func (r *oneByteReader) Read(p []byte) (int, error) { … }

// HalfReader returns a Reader that implements Read
// by reading half as many requested bytes from r.
func HalfReader(r io.Reader) io.Reader { … }

type halfReader …

func (r *halfReader) Read(p []byte) (int, error) { … }

// DataErrReader changes the way errors are handled by a Reader. Normally, a
// Reader returns an error (typically EOF) from the first Read call after the
// last piece of data is read. DataErrReader wraps a Reader and changes its
// behavior so the final error is returned along with the final data, instead
// of in the first call after the final data.
func DataErrReader(r io.Reader) io.Reader { … }

type dataErrReader …

func (r *dataErrReader) Read(p []byte) (n int, err error) { … }

var ErrTimeout …

// TimeoutReader returns [ErrTimeout] on the second read
// with no data. Subsequent calls to read succeed.
func TimeoutReader(r io.Reader) io.Reader { … }

type timeoutReader …

func (r *timeoutReader) Read(p []byte) (int, error) { … }

// ErrReader returns an [io.Reader] that returns 0, err from all Read calls.
func ErrReader(err error) io.Reader { … }

type errReader …

func (r *errReader) Read(p []byte) (int, error) { … }

type smallByteReader …

func (r *smallByteReader) Read(p []byte) (int, error) { … }

// TestReader tests that reading from r returns the expected file content.
// It does reads of different sizes, until EOF.
// If r implements [io.ReaderAt] or [io.Seeker], TestReader also checks
// that those operations behave as they should.
//
// If TestReader finds any misbehaviors, it returns an error reporting them.
// The error text may span multiple lines.
func TestReader(r io.Reader, content []byte) error { … }