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Description:

test process

A package for testing subprocesses.
This exposes a TestProcess class that wraps dart:io's
Process class and makes it easy to read standard output
line-by-line. TestProcess works the same as Process in many ways, but there
are a few major differences.
Standard Output #
Process.stdout and Process.stderr are binary streams, which is the most
general API but isn't the most helpful when working with a program that produces
plain text. Instead, TestProcess.stdout and
TestProcess.stderr emit a string for each line of output the process
produces. What's more, they're StreamQueues, which means
they provide a pull-based API. For example:
import 'package:test/test.dart';
import 'package:test_process/test_process.dart';

void main() {
test('pub get gets dependencies', () async {
// TestProcess.start() works just like Process.start() from dart:io.
var process = await TestProcess.start('dart', ['pub', 'get']);

// StreamQueue.next returns the next line emitted on standard out.
var firstLine = await process.stdout.next;
expect(firstLine, equals('Resolving dependencies...'));

// Each call to StreamQueue.next moves one line further.
String next;
do {
next = await process.stdout.next;
} while (next != 'Got dependencies!');

// Assert that the process exits with code 0.
await process.shouldExit(0);
});
}
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The test package's stream matchers have built-in support for
StreamQueues, which makes them perfect for making assertions about a process's
output. We can use this to clean up the previous example:
import 'package:test/test.dart';
import 'package:test_process/test_process.dart';

void main() {
test('pub get gets dependencies', () async {
var process = await TestProcess.start('dart', ['pub', 'get']);

// Each stream matcher will consume as many lines as it matches from a
// StreamQueue, and no more, so it's safe to use them in sequence.
await expectLater(process.stdout, emits('Resolving dependencies...'));

// The emitsThrough matcher matches and consumes any number of lines, as
// long as they end with one matching the argument.
await expectLater(process.stdout, emitsThrough('Got dependencies!'));

await process.shouldExit(0);
});
}
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If you want to access the standard output streams without consuming any values
from the queues, you can use the stdoutStream() and
stderrStream() methods. Each time you call one of these, it
produces an entirely new stream that replays the corresponding output stream
from the beginning, regardless of what's already been produced by stdout,
stderr, or other calls to the stream method.
Signals and Termination #
The way signaling works is different from dart:io as well. TestProcess still
has a kill() method, but it defaults to SIGKILL on Mac OS and Linux
to ensure (as best as possible) that processes die without leaving behind
zombies. If you want to send a particular signal (which is unsupported on
Windows), you can do so by explicitly calling signal().
In addition to exitCode, which works the same as in dart:io,
TestProcess also adds a new method named shouldExit(). This
lets tests wait for a process to exit, and (if desired) assert what particular
exit code it produced.
Debugging Output #
When a test using TestProcess fails, it will print all the output produced by
that process. This makes it much easier to figure out what went wrong and why.
The debugging output uses a header based on the process's invocation by
default, but you can pass in custom description parameters to
TestProcess.start() to control the headers.
TestProcess will also produce debugging output as the test runs if you pass
forwardStdio: true to TestProcess.start(). This can be particularly useful
when you're using an interactive debugger and you want to figure out what a
process is doing before the test finishes and the normal debugging output is
printed.