The test
WC_Tests_API_Functions::test_wc_rest_upload_image_from_url_should_download_image_and_return_array()
was failing on Travis with the error below due images being kept on
accros different tests. To fix this problem, this commit makes sure that
every test that creates an image, removes it after the assertions.
```
1) WC_Tests_API_Functions::test_wc_rest_upload_image_from_url_should_download_image_and_return_array
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
Array (
- 'file' => '/tmp/wordpress/wp-content/uploads/2020/01/Dr1Bczxq4q.png'
- 'url' => 'http://example.org/wp-content/uploads/2020/01/Dr1Bczxq4q.png'
+ 'file' => '/tmp/wordpress/wp-content/uploads/2020/01/Dr1Bczxq4q-3.png'
+ 'url' => 'http://example.org/wp-content/uploads/2020/01/Dr1Bczxq4q-3.png'
/home/travis/build/woocommerce/woocommerce-rest-api/unit-tests/Tests/Version3/functions.php:113
```
(https://travis-ci.org/woocommerce/woocommerce-rest-api/jobs/634921426#L719)
This implements two changes to WC_Tests_REST_System_Status test class:
- It simplifies the tests by setting the user in the setUp method
instead of in each test.
- Improves the performance of the tests by creating a new admin user
only once when the class is instantiated instead of once for every
single test that is executed.
Claudio Sanches
Rodrigo Primo
Christopher Allford
Mike Jolley
