Package iotest implements Readers and Writers useful mainly for testing.
ErrTimeout is a fake timeout 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.
ErrReader returns an io.Reader that returns 0, err from all Read calls.
// A reader that always returns a custom error. r := iotest.ErrReader(errors.New("custom error")) n, err := r.Read(nil) fmt.Printf("n: %d\nerr: %q\n", n, err)
n: 0 err: "custom error"
HalfReader returns a Reader that implements Read by reading half as many requested bytes from r.
NewReadLogger returns a reader that behaves like r except that it logs (using log.Printf) each read to standard error, printing the prefix and the hexadecimal data read.
NewWriteLogger returns a writer that behaves like w except that it logs (using log.Printf) each write to standard error, printing the prefix and the hexadecimal data written.
OneByteReader returns a Reader that implements each non-empty Read by reading one byte from r.
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.
TimeoutReader returns ErrTimeout on the second read with no data. Subsequent calls to read succeed.
TruncateWriter returns a Writer that writes to w but stops silently after n bytes.