Add tests for cachefile truthiness

tests/test_cachefiles.py

@@ -1,18 +1,41 @@
 from imagekit.cachefiles import ImageCacheFile
 from nose.tools import raises
 from .imagegenerators import TestSpec
-from .utils import assert_file_is_falsy
+from .utils import (assert_file_is_truthy, assert_file_is_falsy,
+                    DummyAsyncCacheFileBackend, get_unique_image_file)
 
 
-def test_no_source():
+def test_no_source_falsiness():
     """
-    Ensure sourceless specs are falsy.
+    Ensure cache files generated from sourceless specs are falsy.
+
     """
     spec = TestSpec(source=None)
     file = ImageCacheFile(spec)
     assert_file_is_falsy(file)
 
 
+def test_sync_backend_truthiness():
+    """
+    Ensure that a cachefile with a synchronous cache file backend (the default)
+    is truthy.
+
+    """
+    spec = TestSpec(source=get_unique_image_file())
+    file = ImageCacheFile(spec)
+    assert_file_is_truthy(file)
+
+
+def test_async_backend_falsiness():
+    """
+    Ensure that a cachefile with an asynchronous cache file backend is falsy.
+
+    """
+    spec = TestSpec(source=get_unique_image_file())
+    file = ImageCacheFile(spec, cachefile_backend=DummyAsyncCacheFileBackend())
+    assert_file_is_falsy(file)
+
+
 @raises(TestSpec.MissingSource)
 def test_no_source_error():
     spec = TestSpec(source=None)

tests/utils.py

@@ -3,9 +3,11 @@ import os
 from django.conf import settings
 from django.core.files import File
 from django.template import Context, Template
+from imagekit.cachefiles.backends import Simple, CacheFileState
 from imagekit.lib import Image, StringIO
 from nose.tools import assert_true, assert_false
 import pickle
+from tempfile import NamedTemporaryFile
 from .models import Photo
 
 
@@ -21,6 +23,12 @@ def get_image_file():
     return open(path, 'r+b')
 
 
+def get_unique_image_file():
+    file = NamedTemporaryFile()
+    file.write(get_image_file().read())
+    return file
+
+
 def create_image():
     return Image.open(get_image_file())
 
@@ -62,3 +70,13 @@ def assert_file_is_falsy(file):
 
 def assert_file_is_truthy(file):
     assert_true(bool(file), 'File is not truthy')
+
+
+class DummyAsyncCacheFileBackend(Simple):
+    """
+    A cache file backend meant to simulate async generation (by marking the
+    file as pending but never actually creating it).
+
+    """
+    def _generate(self, file):
+        self.set_state(file, CacheFileState.PENDING)