This commit adds support to the `wasm-bindgen-test-runner` binary to
perform headless testing via browsers. The previous commit introduced a
local server to serve up files and run tests in a browser, and this
commit adds support for executing that in an automated fashion.
The general idea here is that each browser has a binary that implements
the WebDriver specification. These binaries (typically `foodriver` for
the browser "Foo") are interfaced with using HTTP and JSON messages. The
implementation was simple enough and the crates.io support was lacking
enough that a small implementation of the WebDriver protocol was added
directly to this crate.
Currently Firefox (`geckodriver`), Chrome (`chromedriver`), and Safari
(`safaridriver`) are supported for running tests. The test harness will
recognize env vars like `GECKODRIVER=foo` to specifically use one or
otherwise detects the first driver in `PATH`. Eventually we may wish to
automatically download a driver if one isn't found, but that isn't
implemented yet.
Headless testing is turned on with the `CI=1` env var currently to be
amenable with things like Travis and AppVeyor, but this may wish to grow
an explicit option to run headless tests in the future.
The JS iterator protocol uses duck typing and we don't need separate
ArrayIterator and SetIterator etc types, we can have a single iterator type for
the whole protocol.
