[16] Tests for logging to validate 1.4.10 (#1)

-removes dependency to log4j binding for slf4j, so clients can choose a different binding
-adds dependency to slf4j-api
-adds test logging binding by adding (test) dependency to uk.org.lidalia:slf4j-test
-adds (test) dependency to assertj for better readable assertions

Author: lopitz

lib/build.gradle

@@ -26,15 +26,17 @@ repositories {
 }
 
 dependencies {
-    implementation 'org.slf4j:slf4j-log4j12:1.7.36'
     implementation 'com.fasterxml.jackson.core:jackson-databind:2.13.2.1'
+    implementation 'org.slf4j:slf4j-api:1.7.36'
 
     // This dependency is used internally, and not exposed to consumers on their own compile classpath.
     implementation 'com.google.guava:guava:30.1.1-jre'
 
     // Use JUnit Jupiter for testing.
     testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
     testImplementation 'org.mockito:mockito-core:4+'
+    testImplementation 'uk.org.lidalia:slf4j-test:1.1.0'
+    testImplementation 'org.assertj:assertj-core:3.23.1'
 
     // This dependency is exported to consumers, that is to say found on their compile classpath.
     api 'org.apache.commons:commons-math3:3.6.1'
@@ -121,4 +123,4 @@ publishing {
             url = repo_url
         }
     }
-}
+}

lib/src/test/java/dev/openfeature/javasdk/FlagEvaluationSpecTests.java

@@ -1,16 +1,20 @@
 package dev.openfeature.javasdk;
 
-import org.junit.jupiter.api.Disabled;
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.*;
+import org.slf4j.*;
+import uk.org.lidalia.slf4jtest.*;
 
 import java.util.List;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.*;
 import static org.mockito.Mockito.*;
 
-public class FlagEvaluationSpecTests {
+class FlagEvaluationSpecTests {
 
-    Client _client() {
+    private static final TestLogger TEST_LOGGER = TestLoggerFactory.getTestLogger(OpenFeatureClient.class);
+
+    private Client _client() {
         OpenFeatureAPI api = OpenFeatureAPI.getInstance();
         api.setProvider(new NoOpProvider());
         return api.getClient();
@@ -160,10 +164,16 @@ Client _client() {
         FlagEvaluationDetails<Boolean> details = c.getBooleanDetails("key", false);
         assertEquals("BORK", details.getErrorCode());
     }
+
     @Specification(number="1.4.10", text="In the case of abnormal execution, the client SHOULD log an informative error message.")
-    @Disabled("Not actually sure how to mock out the slf4j logger")
     @Test void log_on_error() throws NotImplementedException {
-        throw new NotImplementedException("Dunno.");
+        TEST_LOGGER.clear();
+        OpenFeatureAPI api = OpenFeatureAPI.getInstance();
+        api.setProvider(new AlwaysBrokenProvider());
+        Client c = api.getClient();
+        FlagEvaluationDetails<Boolean> result = c.getBooleanDetails("test", false);
+        assertEquals(Reason.ERROR, result.getReason());
+        assertThat(TEST_LOGGER.getLoggingEvents()).contains(LoggingEvent.error("Unable to correctly evaluate flag with key {} due to exception {}", "test", "BORK"));
     }