SimpleTest fails its own tests on install

Trying to get SimpleTest working, and driving myself insane.

Firstly, SimpleTest will not activate as it says that it cannot locate the settings.php file, which is located in /sites/default/settings.php. I found that modifying lines 140 and 152 of simpletest.install to add "/sites/default/" enabled installation:

Line 140:
if (strpos(file_get_contents(file_directory_path() . '/../sites/default/settings.php'), trim($find)) !== FALSE) {

Line 152:

array('%settings' => realpath(file_directory_path() . '/../sites/default/settings.php'),<code>

Given the following, however, I realise there might be something very wrong with having done that—I was just trying to figure out how to fix the install originally...

So, having installed SimpleTest I tried to run its own tests... It reported first

<code>The directory sites/default/files/simpletest852693 has been created.
The directory sites/default/files/simpletest28608 has been created.
The tests have finished running.

but then said
warning: Invalid argument supplied for foreach() in /Users/Duncan/Wavelength/Design/Development/catalyst.ac.nz/catalyst.ac.nz/sites/all/modules/simpletest/simpletest.test on line 149.

It reported ten of these errors, eight referring to line 149 and two referring to line 129.

Then, in the tests themselves, it reported 27 passes, 19 fails, 0 exceptions:
Created role of name: simpletest_HV_a, id: 3 Role drupal_web_test_case.php 481 _drupalCreateRole
Created permissions: administer unit tests Role drupal_web_test_case.php 481 _drupalCreateRole
User created with name simpletest_Beij and pass uuyHu6R4PH User login simpletest.test 38 drupalCreateUser
GET to http://catalyst.ac.nz, response is 5364 bytes. Browser drupal_web_test_case.php 748 curlExec
GET to http://catalyst.ac.nz/user, response is 3855 bytes. Browser drupal_web_test_case.php 822 curlExec
Valid HTML found on "http://catalyst.ac.nz/user" Browser drupal_web_test_case.php 864 parse
POST to http://catalyst.ac.nz/user, response is 3855 bytes. Browser drupal_web_test_case.php 896 curlExec
Found name: simpletest_Beij Other simpletest.test 39 drupalLogin
No blocked message at login page User login simpletest.test 39 drupalLogin
No reserved message at login page User login simpletest.test 39 drupalLogin
GET to http://catalyst.ac.nz/node, response is 5364 bytes. Browser drupal_web_test_case.php 822 curlExec
Valid HTML found on "http://catalyst.ac.nz/node" Browser drupal_web_test_case.php 1070 parse
Site title matches. Other drupal_web_test_case.php 274 testInternalBrowser
GET to http://catalyst.ac.nz/install.php, response is 0 bytes. Browser drupal_web_test_case.php 822 curlExec
Cannot access install.php with a "simpletest" user-agent header. Browser drupal_web_test_case.php 274 testInternalBrowser
Created role of name: simpletest_yn8b, id: 3 Role drupal_web_test_case.php 481 _drupalCreateRole
Created permissions: administer unit tests Role drupal_web_test_case.php 481 _drupalCreateRole
User created with name simpletest_OPO4 and pass sd5CM3QWP8 User login simpletest.test 38 drupalCreateUser
GET to http://catalyst.ac.nz, response is 5364 bytes. Browser drupal_web_test_case.php 748 curlExec
GET to http://catalyst.ac.nz/user, response is 3855 bytes. Browser drupal_web_test_case.php 822 curlExec
Valid HTML found on "http://catalyst.ac.nz/user" Browser drupal_web_test_case.php 864 parse
POST to http://catalyst.ac.nz/user, response is 3855 bytes. Browser drupal_web_test_case.php 896 curlExec
Found name: simpletest_OPO4 Other simpletest.test 39 drupalLogin
No blocked message at login page User login simpletest.test 39 drupalLogin
No reserved message at login page User login simpletest.test 39 drupalLogin
GET to http://catalyst.ac.nz/admin/build/testing, response is 4031 bytes. Browser drupal_web_test_case.php 822 curlExec
Valid HTML found on "http://catalyst.ac.nz/admin/build/testing" Browser drupal_web_test_case.php 864 parse
Failed to set field SimpleTestTestCase to 1 Other simpletest.test 85 drupalPost
Found the Run tests button Other simpletest.test 85 drupalPost
Found the requested form fields at Other simpletest.test 85 drupalPost
Found assertion {"SimpleTest pass.", "Other", "Pass"}. Other simpletest.test 89 confirmStubTestResults
Found assertion {"SimpleTest fail.", "Other", "Fail"}. Other simpletest.test 89 confirmStubTestResults
Found assertion {"Created permissions: access content", "Role", "Pass"}. Other simpletest.test 89 confirmStubTestResults
Found assertion {"Invalid permission invalid permission.", "Role", "Fail"}. Other simpletest.test 89 confirmStubTestResults
Found test ID in results. Other simpletest.test 89 confirmStubTestResults
GET to http://catalyst.ac.nz/admin/build/testing, response is 4031 bytes. Browser drupal_web_test_case.php 822 curlExec
Valid HTML found on "http://catalyst.ac.nz/admin/build/testing" Browser drupal_web_test_case.php 864 parse
Failed to set field SimpleTestTestCase to 1 Other simpletest.test 85 drupalPost
Found the Run tests button Other simpletest.test 85 drupalPost
Found the requested form fields at Other simpletest.test 85 drupalPost
Found assertion {"SimpleTest pass.", "Other", "Pass"}. Other simpletest.test 89 confirmStubTestResults
Found assertion {"SimpleTest fail.", "Other", "Fail"}. Other simpletest.test 89 confirmStubTestResults
Found assertion {"Created permissions: access content", "Role", "Pass"}. Other simpletest.test 89 confirmStubTestResults
Found assertion {"Invalid permission invalid permission.", "Role", "Fail"}. Other simpletest.test 89 confirmStubTestResults
Found test ID in results. Other simpletest.test 89 confirmStubTestResults
Test ID is incrementing. Other drupal_web_test_case.php 274 testWebTestRunner

I guess I had hoped that SimpleTest would at least pass its own tests on first try! I've tried reinstalling SimpleTest (after proper uninstall), I've tried installing and running it with all non-core modules turned off... same result.

Probably I broke it at A and so am getting B. But I'd love some sane advice. :)