Add tests for new source concept

Ok, the attached patch adds tests for the first and last point of the above list. Incremental improvements is probably the best way forward here.

The "performance test" does send a newsletter to 100 recipients and then calculates the used time. Locally, cached took around 2,5s while non-cached took around 4s. This is with a very simple body, so this is actually the base. It can be assumed that non-cached gets slower and slower, the more complex your body is, while cached stays relatively constant as it need to do the build only once.

I'll upload a second version of the patch, which prints the time as fails to see them on the testbot.

More importantly, the patch fixes a number of bugs:

- The cached source class is wrong in the hook implementation, which leads to a fatal error when trying to send the test. Fixed and confirmed through the tests
- The build:body:$format cache was not written properly, causing it to be re-generated always. Not directly tested, as this is kinda tricky.

Changes:
- Removed the $accounts argument from simplenews_add_node_to_spool(). It wasn't actually used anymore.
- There is now a SimplenewsSourceInterface::getPlainFooter() method and the getBody() and getFooter() methods are supposed to return the correct content based getFormat(). What they actually already did, it just hadn't been called like this nor documented. Fixed and tested.
- That plaintext footer is now also appended to the plaintext version, which is generated if the format is html.

Looks like the test source implementation can't lie in the test file...

Just noticed another bug, the build isn't internally cached. This is bad because it's used like 4 times during a single mail.

- build is now properly cached (only per mail, outside of the cache handling)
- Refactored and fixed plaintext/html handling
- Removed a unused function, left-over from an earlier source implementation (poor kitten)

Commited, back to active for the remaining test cases.

Updated issue summary.

+++ b/tests/simplenews.testundefined
@@ -2794,4 +2794,58 @@ class SimplenewsSourceTestCase extends SimplenewsTestCase {
+    $this->setUpSubscribers(100);

Its enough if we add 3 subscribers, we don't need more.

+++ b/tests/simplenews.testundefined
@@ -2794,4 +2794,58 @@ class SimplenewsSourceTestCase extends SimplenewsTestCase {
+    $edit = array(
+        'title' => $this->randomName(),
+        'body[und][0][value]' => "Mail token: <strong>[simplenews-subscriber:mail]</strong>",

Incorrect indentation.

+++ b/tests/simplenews.testundefined
@@ -2794,4 +2794,58 @@ class SimplenewsSourceTestCase extends SimplenewsTestCase {
+    catch (Exception $e) {
+      // Intentionaly left blank.

You can add a $this->pass('Exception thrown when invalid source implementation is configured').

+++ b/tests/simplenews.testundefined
@@ -2794,4 +2794,58 @@ class SimplenewsSourceTestCase extends SimplenewsTestCase {
+      // Make sure that the same mail was used in the body token as it has been
+      // sent to. Also verify that the mail is plaintext.
+      $this->assertTrue(strpos($mail['subject'], 'the subject') !== FALSE);

The comment should probably be updated say what we are actually testing: that the test source was used and not the default one.

+++ b/includes/simplenews.source.incundefined
@@ -299,6 +307,10 @@ class SimplenewsSpool implements SimplenewsSpoolInterface {
+    if ($interfaces && !in_array('SimplenewsSourceNodeInterface', $interfaces)) {
+      throw new Exception("Source must implement SimplenewsSouceNodeInterface");

Should actually be !$interfaces || ... .

Because if it does not implement any interfaces at all, it is wrong as well.

Oh, and the as discussed, a bit of documentation would be nice of the spool and source defgroups.

Updated issue summary.