ToolbarIntegrationTest fails randomly on postgres

Drupal 8.1.0, with RefreshLess enabled:

PHPUnit 4.8.11 by Sebastian Bergmann and contributors.

E

Time: 1.32 minutes, Memory: 4.00Mb

There was 1 error:

1) Drupal\Tests\toolbar\FunctionalJavascript\ToolbarIntegrationTest::testToolbarToggling
Zumba\GastonJS\Exception\JavascriptError: One or more errors were raised in the Javascript code on the page.
            If you don't care about these errors, you can ignore them by
            setting js_errors: false in your Poltergeist configuration (see documentation for details).
AjaxError: 
An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /toolbar/subtrees/h44VigUWX0CKpfG-F2mSPWyAQ6j34qKtKGcs2os92wg
StatusText: Internal Server Error
ResponseText: {"message":"A fatal error occurred: SQLSTATE[42S02]: Base table or view not found: 1146 Table \u0027drupal.simpletest977695key_value\u0027 doesn\u0027t exist: SELECT 1 AS expression\nFROM \n{key_value} key_value\nWHERE ( (name = :db_condition_placeholder_0) AND (collection = :db_condition_placeholder_1) ); Array\n(\n    [:db_condition_placeholder_0] =\u003E system.theme.files\n    [:db_condition_placeholder_1] =\u003E state\n)\n"}
AjaxError: 
An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /toolbar/subtrees/h44VigUWX0CKpfG-F2mSPWyAQ6j34qKtKGcs2os92wg
StatusText: Internal Server Error
ResponseText: {"message":"A fatal error occurred: SQLSTATE[42S02]: Base table or view not found: 1146 Table \u0027drupal.simpletest977695key_value\u0027 doesn\u0027t exist: SELECT 1 AS expression\nFROM \n{key_value} key_value\nWHERE ( (name = :db_condition_placeholder_0) AND (collection = :db_condition_placeholder_1) ); Array\n(\n    [:db_condition_placeholder_0] =\u003E system.theme.files\n    [:db_condition_placeholder_1] =\u003E state\n)\n"}
    at http://localhost/core/misc/ajax.js?v=8.1.1:965 in error
    at http://localhost/core/misc/ajax.js?v=8.1.1:510 in complete
    at http://localhost/core/assets/vendor/jquery/jquery.min.js?v=2.1.4:2 in j
    at http://localhost/core/assets/vendor/jquery/jquery.min.js?v=2.1.4:2 in fireWith
    at http://localhost/core/assets/vendor/jquery/jquery.min.js?v=2.1.4:4 in x
    at http://localhost/core/assets/vendor/jquery/jquery.min.js?v=2.1.4:4

/var/www/html/vendor/jcalderonzumba/gastonjs/src/Browser/BrowserBase.php:119
/var/www/html/vendor/jcalderonzumba/gastonjs/src/Browser/BrowserBase.php:99
/var/www/html/vendor/jcalderonzumba/gastonjs/src/Browser/BrowserCookieTrait.php:54
/var/www/html/vendor/jcalderonzumba/mink-phantomjs-driver/src/SessionTrait.php:45
/var/www/html/vendor/jcalderonzumba/mink-phantomjs-driver/src/SessionTrait.php:37
/var/www/html/vendor/behat/mink/src/Session.php:78
/var/www/html/vendor/behat/mink/src/Mink.php:186
/var/www/html/core/tests/Drupal/Tests/BrowserTestBase.php:506

FAILURES!
Tests: 1, Assertions: 10, Errors: 1.

With RefreshLess disabled:

PHPUnit 4.8.11 by Sebastian Bergmann and contributors.

.

Time: 1.52 minutes, Memory: 4.00Mb

OK (1 test, 10 assertions)

My Questions

1. Is it true that SIMPLETEST_BASE_URL is supposed to be set to the URL that I can access my site with (i.e. the default profile) and then Simpletest module will know to serve the testing environment instead of the default environment?

2. What I don't understand is that since the test runs in a separate environment, why would enabling a module on the "default" profile affect tests?

Thanks!