fix: enableAll and disableAll overrides fallback

As discussed in #239 - When all is enabled, we had a bit of a surprising
behaviour where we'd fallback to fallback action for
`isEnabled(featureName, fallback)` even if all was enabled and feature
did not exist.

This PR fixes that, and adds tests to confirm this behaviour is
intentional.

closes: #239

src/main/java/io/getunleash/FakeUnleash.java

@@ -38,7 +38,7 @@ public boolean isEnabled(
     @Override
     public boolean isEnabled(
             String toggleName, BiPredicate<String, UnleashContext> fallbackAction) {
-        if (!features.containsKey(toggleName)) {
+        if ((!enableAll && !disableAll || excludedFeatures.containsKey(toggleName)) && !features.containsKey(toggleName)) {
             return fallbackAction.test(toggleName, UnleashContext.builder().build());
         }
         return isEnabled(toggleName);

src/test/java/io/getunleash/FakeUnleashTest.java

@@ -179,4 +179,25 @@ public void should_countVariant_and_not_throw_an_error() {
         FakeUnleash fakeUnleash = new FakeUnleash();
         fakeUnleash.more().countVariant("toggleName", "variantName");
     }
+
+    @Test
+    public void if_all_is_enabled_should_return_true_even_if_feature_does_not_exist_and_fallback_returns_false() {
+        FakeUnleash fakeUnleash = new FakeUnleash();
+        fakeUnleash.enableAll();
+        assertThat(fakeUnleash.isEnabled("my.non.existing.feature", (name, context) -> false)).isTrue();
+    }
+
+    @Test
+    public void if_all_is_disabled_should_return_false_even_if_feature_does_not_exist_and_fallback_returns_true() {
+        FakeUnleash fakeUnleash = new FakeUnleash();
+        fakeUnleash.disableAll();
+        assertThat(fakeUnleash.isEnabled("my.non.existing.feature", (name, context) -> true)).isFalse();
+    }
+
+    @Test
+    public void all_enabled_and_exclusion_toggle_returns_expected_result() {
+        FakeUnleash fakeUnleash = new FakeUnleash();
+        fakeUnleash.enableAllExcept("my.feature.that.should.be.disabled");
+        assertThat(fakeUnleash.isEnabled("my.feature.that.should.be.disabled", (name, context) -> false)).isFalse();
+    }
 }