test: Reduce usage of singelton within our tests and implementations

pom.xml

@@ -67,6 +67,13 @@
         </dependency>
 
         <!-- test -->
+        <dependency>
+            <groupId>com.tngtech.archunit</groupId>
+            <artifactId>archunit-junit5</artifactId>
+            <version>1.4.0</version>
+            <scope>test</scope>
+        </dependency>
+
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>
@@ -242,12 +249,14 @@
                     <ignoredUnusedDeclaredDependencies>
                         <ignoredUnusedDeclaredDependency>com.github.spotbugs:*</ignoredUnusedDeclaredDependency>
                         <ignoredUnusedDeclaredDependency>org.junit*</ignoredUnusedDeclaredDependency>
+                        <ignoredUnusedDeclaredDependency>com.tngtech.archunit*</ignoredUnusedDeclaredDependency>
                         <ignoredUnusedDeclaredDependency>org.simplify4u:slf4j2-mock*</ignoredUnusedDeclaredDependency>
                     </ignoredUnusedDeclaredDependencies>
                     <ignoredDependencies>
                         <ignoredDependency>com.google.guava*</ignoredDependency>
                         <ignoredDependency>io.cucumber*</ignoredDependency>
                         <ignoredDependency>org.junit*</ignoredDependency>
+                        <ignoredDependency>com.tngtech.archunit*</ignoredDependency>
                         <ignoredDependency>com.google.code.findbugs*</ignoredDependency>
                         <ignoredDependency>com.github.spotbugs*</ignoredDependency>
                         <ignoredDependency>org.simplify4u:slf4j-mock-common:*</ignoredDependency>

src/main/java/dev/openfeature/sdk/OpenFeatureAPI.java

@@ -29,7 +29,7 @@ public class OpenFeatureAPI implements EventBus<OpenFeatureAPI> {
 
     protected OpenFeatureAPI() {
         apiHooks = new ArrayList<>();
-        providerRepository = new ProviderRepository();
+        providerRepository = new ProviderRepository(this);
         eventSupport = new EventSupport();
         transactionContextPropagator = new NoOpTransactionContextPropagator();
     }
@@ -333,7 +333,7 @@ public void shutdown() {
             providerRepository.shutdown();
             eventSupport.shutdown();
 
-            providerRepository = new ProviderRepository();
+            providerRepository = new ProviderRepository(this);
             eventSupport = new EventSupport();
         }
     }

src/main/java/dev/openfeature/sdk/OpenFeatureClient.java

@@ -507,7 +507,7 @@ public Client onProviderStale(Consumer<EventDetails> handler) {
      */
     @Override
     public Client on(ProviderEvent event, Consumer<EventDetails> handler) {
-        OpenFeatureAPI.getInstance().addHandler(domain, event, handler);
+        openfeatureApi.addHandler(domain, event, handler);
         return this;
     }
 
@@ -516,7 +516,7 @@ public Client on(ProviderEvent event, Consumer<EventDetails> handler) {
      */
     @Override
     public Client removeHandler(ProviderEvent event, Consumer<EventDetails> handler) {
-        OpenFeatureAPI.getInstance().removeHandler(domain, event, handler);
+        openfeatureApi.removeHandler(domain, event, handler);
         return this;
     }
 }

src/main/java/dev/openfeature/sdk/ProviderRepository.java

@@ -28,6 +28,11 @@ class ProviderRepository {
         return thread;
     });
     private final Object registerStateManagerLock = new Object();
+    private final OpenFeatureAPI openFeatureAPI;
+
+    public ProviderRepository(OpenFeatureAPI openFeatureAPI) {
+        this.openFeatureAPI = openFeatureAPI;
+    }
 
     FeatureProviderStateManager getFeatureProviderStateManager() {
         return defaultStateManger.get();
@@ -205,7 +210,7 @@ private void initializeProvider(
             FeatureProviderStateManager oldManager) {
         try {
             if (ProviderState.NOT_READY.equals(newManager.getState())) {
-                newManager.initialize(OpenFeatureAPI.getInstance().getEvaluationContext());
+                newManager.initialize(openFeatureAPI.getEvaluationContext());
                 afterInit.accept(newManager.getProvider());
             }
             shutDownOld(oldManager, afterShutdown);

src/test/java/dev/openfeature/sdk/ClientProviderMappingTest.java

@@ -2,17 +2,16 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
-import dev.openfeature.sdk.testutils.FeatureProviderTestUtils;
 import org.junit.jupiter.api.Test;
 
 class ClientProviderMappingTest {
 
     @Test
     void clientProviderTest() {
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
 
-        FeatureProviderTestUtils.setFeatureProvider("client1", new DoSomethingProvider());
-        FeatureProviderTestUtils.setFeatureProvider("client2", new NoOpProvider());
+        api.setProviderAndWait("client1", new DoSomethingProvider());
+        api.setProviderAndWait("client2", new NoOpProvider());
 
         Client c1 = api.getClient("client1");
         Client c2 = api.getClient("client2");

src/test/java/dev/openfeature/sdk/DeveloperExperienceTest.java

@@ -8,7 +8,6 @@
 import static org.mockito.Mockito.verify;
 
 import dev.openfeature.sdk.fixtures.HookFixtures;
-import dev.openfeature.sdk.testutils.FeatureProviderTestUtils;
 import dev.openfeature.sdk.testutils.TestEventsProvider;
 import java.util.Arrays;
 import java.util.HashMap;
@@ -23,7 +22,7 @@ class DeveloperExperienceTest implements HookFixtures {
 
     @Test
     void simpleBooleanFlag() {
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         api.setProviderAndWait(new TestEventsProvider());
         Client client = api.getClient();
         Boolean retval = client.getBooleanValue(flagKey, false);
@@ -34,7 +33,7 @@ void simpleBooleanFlag() {
     void clientHooks() {
         Hook<Boolean> exampleHook = mockBooleanHook();
 
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         api.setProviderAndWait(new TestEventsProvider());
         Client client = api.getClient();
         client.addHooks(exampleHook);
@@ -48,7 +47,7 @@ void evalHooks() {
         Hook<Boolean> clientHook = mockBooleanHook();
         Hook<Boolean> evalHook = mockBooleanHook();
 
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         api.setProviderAndWait(new TestEventsProvider());
         Client client = api.getClient();
         client.addHooks(clientHook);
@@ -69,7 +68,7 @@ void evalHooks() {
     @Test
     void providingContext() {
 
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         api.setProviderAndWait(new TestEventsProvider());
         Client client = api.getClient();
         Map<String, Value> attributes = new HashMap<>();
@@ -86,8 +85,8 @@ void providingContext() {
 
     @Test
     void brokenProvider() {
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
-        FeatureProviderTestUtils.setFeatureProvider(new AlwaysBrokenProvider());
+        OpenFeatureAPI api = new OpenFeatureAPI();
+        api.setProviderAndWait(new AlwaysBrokenProvider());
         Client client = api.getClient();
         FlagEvaluationDetails<Boolean> retval = client.getBooleanDetails(flagKey, false);
         assertEquals(ErrorCode.FLAG_NOT_FOUND, retval.getErrorCode());
@@ -99,23 +98,24 @@ void brokenProvider() {
     @Test
     void providerLockedPerTransaction() {
 
+        final String defaultValue = "string-value";
+        final OpenFeatureAPI api = new OpenFeatureAPI();
+
         class MutatingHook implements Hook {
 
             @Override
             @SneakyThrows
             // change the provider during a before hook - this should not impact the evaluation in progress
             public Optional before(HookContext ctx, Map hints) {
 
-                FeatureProviderTestUtils.setFeatureProvider(TestEventsProvider.newInitializedTestEventsProvider());
+                api.setProviderAndWait(TestEventsProvider.newInitializedTestEventsProvider());
 
                 return Optional.empty();
             }
         }
 
-        final String defaultValue = "string-value";
-        final OpenFeatureAPI api = OpenFeatureAPI.getInstance();
         final Client client = api.getClient();
-        FeatureProviderTestUtils.setFeatureProvider(new DoSomethingProvider());
+        api.setProviderAndWait(new DoSomethingProvider());
         api.addHooks(new MutatingHook());
 
         // if provider is changed during an evaluation transaction it should proceed with the original provider
@@ -132,7 +132,7 @@ public Optional before(HookContext ctx, Map hints) {
     @Test
     void setProviderAndWaitShouldPutTheProviderInReadyState() {
         String domain = "domain";
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         api.setProviderAndWait(domain, new TestEventsProvider());
         Client client = api.getClient(domain);
         assertThat(client.getProviderState()).isEqualTo(ProviderState.READY);
@@ -145,7 +145,7 @@ void setProviderAndWaitShouldPutTheProviderInReadyState() {
     @Test
     void shouldPutTheProviderInStateErrorAfterEmittingErrorEvent() {
         String domain = "domain";
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         TestEventsProvider provider = new TestEventsProvider();
         api.setProviderAndWait(domain, provider);
         Client client = api.getClient(domain);
@@ -161,7 +161,7 @@ void shouldPutTheProviderInStateErrorAfterEmittingErrorEvent() {
     @Test
     void shouldPutTheProviderInStateStaleAfterEmittingStaleEvent() {
         String domain = "domain";
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         TestEventsProvider provider = new TestEventsProvider();
         api.setProviderAndWait(domain, provider);
         Client client = api.getClient(domain);
@@ -177,7 +177,7 @@ void shouldPutTheProviderInStateStaleAfterEmittingStaleEvent() {
     @Test
     void shouldPutTheProviderInStateReadyAfterEmittingReadyEvent() {
         String domain = "domain";
-        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        OpenFeatureAPI api = new OpenFeatureAPI();
         TestEventsProvider provider = new TestEventsProvider();
         api.setProviderAndWait(domain, provider);
         Client client = api.getClient(domain);

src/test/java/dev/openfeature/sdk/EventProviderTest.java

@@ -28,7 +28,7 @@ void setup() {
 
     @AfterAll
     public static void resetDefaultProvider() {
-        OpenFeatureAPI.getInstance().setProviderAndWait(new NoOpProvider());
+        new OpenFeatureAPI().setProviderAndWait(new NoOpProvider());
     }
 
     @Test
@@ -91,7 +91,7 @@ void doesNotThrowWhenOnEmitSame() {
     @DisplayName("should not deadlock on emit called during emit")
     void doesNotDeadlockOnEmitStackedCalls() {
         TestStackedEmitCallsProvider provider = new TestStackedEmitCallsProvider();
-        OpenFeatureAPI.getInstance().setProviderAndWait(provider);
+        new OpenFeatureAPI().setProviderAndWait(provider);
     }
 
     static class TestEventProvider extends EventProvider {