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    <p>This is mostly a summary of (my perspective of) <a href="http://chat.stackoverflow.com/rooms/6954/discussion-between-zerkms-and-deceze">the chat that ensued between me and @zerkms</a>:</p> <p>The point of contention is actually this:</p> <pre><code>public function doSomething($id) { $user = User::getByPhone($this-&gt;pdo, $id); // do something with user return $someData; } </code></pre> <p>This makes it hard to test <code>doSomething</code> since it hardcodes the <code>User</code> class, which may or may not have a lot of dependencies. But this is in fact the same as instantiating the object using a non-static method:</p> <pre><code>public function doSomething($id) { $user = new User; $user-&gt;initializeFromDb($this-&gt;pdo, $id); // do something with user return $someData; } </code></pre> <p>We're not using a static method, but it's still unmockable. Actually, it got worse.<br> The answer is to use a factory:</p> <pre><code>public function doSomething($id) { $user = $this-&gt;UserFactory-&gt;byPhone($id); // do something with user return $someData; } </code></pre> <p>Now the factory can be dependency injected and mocked and the <code>User</code> class is no longer hardcoded. You may or may not think this overkill, but it certainly improves mockability.</p> <p>That does not change the fact though that this factory may very well instantiate the actual user object using a static method:</p> <pre><code>public function byPhone($id) { return User::getByPhone($this-&gt;db, $id); } </code></pre> <p>There's no difference between using a static method or a regular constructor here.</p> <pre><code>$user = new User($db, $id); $user = User::getByPhone($db, $id); </code></pre> <p>Both expressions return an instance of <code>User</code> and both "hardcode" the <code>User</code> class. Which simply needs to happen at some point anyway.</p> <p>For my use case, a <code>static</code> constructor method makes the most sense for the object. And as was demonstrated, <code>static</code> methods are not the problem. Where to <em>call</em> them is the point of contention, not that they exist at all. And I have yet to see a convincing argument for not using static constructors, since they can be wrapped in a factory, which alleviates any problem with mockability, the same as it does for regular object instantiation.</p>
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    1. PO"Static methods are death to testability" - alternatives for alternative constructors?
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    1. PO"Static methods are death to testability" - alternatives for alternative constructors?
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    1. COFor `User::getByPhone()` to have a dependency (like a `PDO` connection) that isn't injected through a method argument, it has to *maintain some sort of state*. Static methods only cause problems when you allow them to maintain/use state. As long as your static methods do not do this, then testability is not affected whatsoever. Please see my answer.
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    2. CO@drrcknlsn That is true, **but**: static methods cannot be mocked. Even if they're 100% dependency injected and the dependencies can be mocked, the static method itself cannot be mocked. This may be important if the method is doing a lot of work or the (injected) dependencies are so extensive that they're difficult to mock. In that case it can be a lot easier to just mock the method itself, which makes it easier to test code *that uses this method*. That is all true. Only **object construction** using a static method is a special case, which does not affect mockability.
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    3. COAfter some abstinence I had a good long look at all the answers here again. Unfortunately none really address the issue I posed in the question, which is about static constructors and why they're bad for testability. I hate to do so with all the good things written by others here, but I'll accept my own answer on this. I have also worked this issue into an article: [How Not To Kill Your Testability Using Statics](http://kunststube.net/static/).
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