1 files changed, 91 insertions, 0 deletions
diff --git a/activesupport/test/cache/behaviors/failure_safety_behavior.rb b/activesupport/test/cache/behaviors/failure_safety_behavior.rb
new file mode 100644
index 0000000000..43b67d81db
--- /dev/null
+++ b/activesupport/test/cache/behaviors/failure_safety_behavior.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+module FailureSafetyBehavior
+  def test_fetch_read_failure_returns_nil
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_nil cache.fetch("foo")
+    end
+  end
+
+  def test_fetch_read_failure_does_not_attempt_to_write
+  end
+
+  def test_read_failure_returns_nil
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_nil cache.read("foo")
+    end
+  end
+
+  def test_read_multi_failure_returns_empty_hash
+    @cache.write_multi("foo" => "bar", "baz" => "quux")
+
+    emulating_unavailability do |cache|
+      assert_equal Hash.new, cache.read_multi("foo", "baz")
+    end
+  end
+
+  def test_write_failure_returns_false
+    emulating_unavailability do |cache|
+      assert_equal false, cache.write("foo", "bar")
+    end
+  end
+
+  def test_write_multi_failure_not_raises
+    emulating_unavailability do |cache|
+      assert_nothing_raised do
+        cache.write_multi("foo" => "bar", "baz" => "quux")
+      end
+    end
+  end
+
+  def test_fetch_multi_failure_returns_fallback_results
+    @cache.write_multi("foo" => "bar", "baz" => "quux")
+
+    emulating_unavailability do |cache|
+      fetched = cache.fetch_multi("foo", "baz") { |k| "unavailable" }
+      assert_equal Hash["foo" => "unavailable", "baz" => "unavailable"], fetched
+    end
+  end
+
+  def test_delete_failure_returns_false
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_equal false, cache.delete("foo")
+    end
+  end
+
+  def test_exist_failure_returns_false
+    @cache.write("foo", "bar")
+
+    emulating_unavailability do |cache|
+      assert_not cache.exist?("foo")
+    end
+  end
+
+  def test_increment_failure_returns_nil
+    @cache.write("foo", 1, raw: true)
+
+    emulating_unavailability do |cache|
+      assert_nil cache.increment("foo")
+    end
+  end
+
+  def test_decrement_failure_returns_nil
+    @cache.write("foo", 1, raw: true)
+
+    emulating_unavailability do |cache|
+      assert_nil cache.decrement("foo")
+    end
+  end
+
+  def test_clear_failure_returns_nil
+    emulating_unavailability do |cache|
+      assert_nil cache.clear
+    end
+  end
+end