dominictarr/ stream-spec
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Description
executable specification for Stream (make testing streams easy)
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StreamSpec
Automatic checking of the Stream implementations.
stream-specinstruments your stream to verify that it has correct behaviour. All you need to do to test a stream is to wrap it with
stream-spec, and then pipe some test data through it. it's purpose it to make it easy to test user-land streams have correct behavour.
correct stream behaviour illustrated
correct stream behaviour explained
stream api design style
a simple test
using stream-tester
var spec = require('stream-spec')
var tester = require('stream-tester')
spec(stream)
.through({strict: true})
.validateOnExit()
tester.createRandomStream(function () {
return 'line ' + Math.random() + '\n'
}, 1000)
.pipe(stream)
.pipe(tester.createPauseStream())
send 1000 random lines through the stream and check that it buffers on pause.
types of Stream
Writable (but not readable)
a
WritableStreammust implement
write,
end,
destroyand emit
'drain'if it pauses, and
'close'after the stream ends, or is destroyed.
If the stream is sync (does no io) it probably does not need to pause, so the
write()should never equal
false
spec(stream) .writable() .drainable() .validateOnExit()
Readable (but not writable)
a
ReadableStreammust emit
'data',
'end', and implement
destroy, and
'close'after the stream ends, or is destroyed. is strongly recommended to implement
pauseand
resume
If the option
{strict: true} is passed, it means the stream is not allowed to emit
'data'or
'end'when the stream is paused.
If the option
{end: false} is passed, then end may not be emitted.
spec(stream)
.readable()
.pausable({strict: true})) //strict is optional.
.validateOnExit()
Through (sync writable and readable, aka: 'filter')
A
Streamthat is both readable and writable, and where the input is processed and then emitted as output, more or less directly. Example, zlib. contrast this with duplex stream.
when you call
pause()on a
ThroughStream, it should change it into a paused state on the writable side also, and
write()===false. Calling
resume()should cause
'drain'to be emitted eventually.
If the option
{strict: true} is passed, it means the stream is not allowed to emit
'data'or
'end'when the stream is paused.
spec(stream)
.through({strict: true}) //strict is optional.
.validateOnExit()
Duplex
A
Streamthat is both readable and writable, but the streams go off to some other place or thing, and are not coupled directly. The readable and writable side of a
DuplexStreameach have their own pause state.
If the option
{strict: true} is passed, it means the stream is not allowed to emit
'data'or
'end'when the stream is paused.
spec(stream)
.duplex({strict: true})
.validateOnExit()
other options
spec(stream, name) //use name as the name of the stream in error messages.spec(stream, { name: name, //same as above. strict: true, //'data' nor 'end' may be emitted when paused. error: true, //this stream must error. error: false, //this stream must not error. //if neither error: boolean option is passed, the stream may error. })