compare method Null safety
Compares the rendered pixels of size
height that is being
rendered on the top left of the screen against the golden file identified
The returned future completes with a boolean value that indicates whether the pixels rendered on screen match the golden file's pixels.
In the case of comparison mismatch, the comparator may choose to throw a TestFailure if it wants to control the failure message, often in the form of a ComparisonResult that provides detailed information about the mismatch.
The method by which
golden is located and by which its bytes are loaded
is left up to the implementation class. For instance, some implementations
may load files from the local file system, whereas others may load files
over the network or from a remote repository.
Future<bool> compare(double width, double height, Uri golden);