Mostly remove bad test

This test was attempting to test how cache keys work by modifying the
templates and seeing when that cache was fresh. This doesn't actually
work for real Resolvers, only FixtureResolver, and isn't desirable. We
absolutely want to share templates if they resolve to the same file.

Instead, this simplifies the test to only check that we get the correct
template for the locale we request.

actionview/test/template/lookup_context_test.rb

@@ -190,33 +190,30 @@ class LookupContextTest < ActiveSupport::TestCase
     assert_equal 3, keys.uniq.size
   end
 
-  test "gives the key forward to the resolver, so it can be used as cache key" do
-    @lookup_context = build_lookup_context(ActionView::FixtureResolver.new("test/_foo.erb" => "Foo"), {})
+  test "uses details as part of cache key" do
+    fixtures = {
+      "test/_foo.erb" => "Foo",
+      "test/_foo.da.erb" => "Bar",
+    }
+    @lookup_context = build_lookup_context(ActionView::FixtureResolver.new(fixtures), {})
+
     template = @lookup_context.find("foo", %w(test), true)
+    original_template = template
     assert_equal "Foo", template.source
 
-    # Now we are going to change the template, but it won't change the returned template
-    # since we will hit the cache.
-    @lookup_context.view_paths.first.data["test/_foo.erb"] = "Bar"
+    # We should get the same template
     template = @lookup_context.find("foo", %w(test), true)
-    assert_equal "Foo", template.source
+    assert_same original_template, template
 
-    # This time we will change the locale. The updated template should be picked since
-    # lookup_context generated a new key after we changed the locale.
+    # Using a different locale we get a different view
     @lookup_context.locale = :da
     template = @lookup_context.find("foo", %w(test), true)
     assert_equal "Bar", template.source
 
-    # Now we will change back the locale and it will still pick the old template.
-    # This is expected because lookup_context will reuse the previous key for :en locale.
+    # Using en we get the original view
     @lookup_context.locale = :en
     template = @lookup_context.find("foo", %w(test), true)
-    assert_equal "Foo", template.source
-
-    # Finally, we can expire the cache. And the expected template will be used.
-    @lookup_context.view_paths.first.clear_cache
-    template = @lookup_context.find("foo", %w(test), true)
-    assert_equal "Bar", template.source
+    assert_same original_template, template
   end
 
   test "can disable the cache on demand" do