LibTest/core/String/String.fromEnvironment_A01_t01 should expect the empty string

[eernstg]

Said test expects new String.fromEnvironment(v) to evaluate to null when v is a string which is not defined in the environment.

However, with the upcoming changes here, it will evaluate to the empty string rather than null, so the test needs to be updated to expect that.

This change is being backported, so the change needs to be made in the pre-nnbd branch, but it will also affect the master branch version, so both tests need to be updated.

[eernstg]

Note that the changes being backported have not all been landed, so it may be a good idea to check the corresponding CL in order to see that the tools are actually in a state where the change has taken place.

[eernstg]

A similar change is needed in co19_2/LibTest/core/int/int.fromEnvironment_A01_t01.dart, as well as in the corresponding test from the master branch. It might be useful to add a test case where a defaultValue is passed, making this test similar to the one for String which is mentioned above.

[eernstg]

Here is the CL where the breaking change is performed: https://dart-review.googlesource.com/c/sdk/+/140640. So when that change lands, the above changes to the tests are needed.

[eernstg]

Said CL is now landing, so the changes are needed now.

[sgrekhov]

Fixed in both branches