Upon failure the log messages appear to be confusingly misleading. From the stack trace in JENKINS-59397.

Creating an upload resource.
io.jenkins.plugins.appcenter.AppCenterException: Create upload resource unsuccessful:
at io.jenkins.plugins.appcenter.task.internal.CreateUploadResourceTask.lambda$execute$0(CreateUploadResourceTask.java:48)
at java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:760)
at java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:736)
at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
at java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:1977)
at retrofit2.CompletableFutureCallAdapterFactory$BodyCallAdapter$2.onFailure(CompletableFutureCallAdapterFactory.java:86)
at retrofit2.OkHttpCall$1.callFailure(OkHttpCall.java:141)
at retrofit2.OkHttpCall$1.onFailure(OkHttpCall.java:136)
at okhttp3.RealCall$AsyncCall.execute(RealCall.java:215)
at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.UnknownHostException: api.appcenter.ms: unknown error
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928)
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323)
at java.net.InetAddress.getAllByName0(InetAddress.java:1276)
at java.net.InetAddress.getAllByName(InetAddress.java:1192)
at java.net.InetAddress.getAllByName(InetAddress.java:1126)
at okhttp3.Dns$1.lookup(Dns.java:40)
at okhttp3.internal.connection.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:185)
at okhttp3.internal.connection.RouteSelector.nextProxy(RouteSelector.java:149)
at okhttp3.internal.connection.RouteSelector.next(RouteSelector.java:84)
at okhttp3.internal.connection.StreamAllocation.findConnection(StreamAllocation.java:214)
at okhttp3.internal.connection.StreamAllocation.findHealthyConnection(StreamAllocation.java:135)
at okhttp3.internal.connection.StreamAllocation.newStream(StreamAllocation.java:114)
at okhttp3.internal.connection.ConnectInterceptor.intercept(ConnectInterceptor.java:42)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
at okhttp3.internal.cache.CacheInterceptor.intercept(CacheInterceptor.java:93)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
at okhttp3.internal.http.BridgeInterceptor.intercept(BridgeInterceptor.java:93)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
at okhttp3.internal.http.RetryAndFollowUpInterceptor.intercept(RetryAndFollowUpInterceptor.java:126)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
at io.jenkins.plugins.appcenter.api.AppCenterServiceFactory.lambda$createAppCenterService$0(AppCenterServiceFactory.java:66)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
at okhttp3.logging.HttpLoggingInterceptor.intercept(HttpLoggingInterceptor.java:225)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:147)
at okhttp3.internal.http.RealInterceptorChain.proceed(RealInterceptorChain.java:121)
at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:254)
at okhttp3.RealCall$AsyncCall.execute(RealCall.java:200)
... 4 more
Create upload resource successful.
io.jenkins.plugins.appcenter.AppCenterException: Upload to AppCenter failed.
at io.jenkins.plugins.appcenter.task.UploadTask.call(UploadTask.java:56)
at io.jenkins.plugins.appcenter.task.UploadTask.call(UploadTask.java:17)
at hudson.FilePath.act(FilePath.java:1160)
at io.jenkins.plugins.appcenter.AppCenterRecorder.uploadToAppCenter(AppCenterRecorder.java:131)
at io.jenkins.plugins.appcenter.AppCenterRecorder.perform(AppCenterRecorder.java:118)
at hudson.tasks.BuildStepCompatibilityLayer.perform(BuildStepCompatibilityLayer.java:81)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:744)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:690)
at hudson.model.Build$BuildExecution.post2(Build.java:186)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:635)
at hudson.model.Run.execute(Run.java:1843)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:97)
at hudson.model.Executor.run(Executor.java:429)

Notice that there is both Create upload resource unsuccessful and Create upload resource successful messages in the output. This cannot be the case.

Acceptance criteria:

1. Tests for all of the internal Tasks are updated to specifically assert the correct log output and the specifically assert the lack of the incorrect log output.
2. All internal tasks log success / failures correctly.