Minor Api testing improvements (#8687)

* Add missing backtests/read null check

* Improve SPDB error message

Author: Martin-Molinero

Api/Api.cs

@@ -525,6 +525,12 @@ public Backtest ReadBacktest(int projectId, string backtestId, bool getCharts =
 
             ApiConnection.TryRequest(request, out BacktestResponseWrapper result);
 
+            if (result == null)
+            {
+                // api call failed
+                return null;
+            }
+
             if (!result.Success)
             {
                 // place an empty place holder so we can return any errors back to the user and not just null

Common/Messages/Messages.Securities.cs

@@ -924,7 +924,7 @@ public static class SecurityService
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             public static string SymbolNotFoundInSymbolPropertiesDatabase(QuantConnect.Symbol symbol)
             {
-                return $"Symbol could not be found in the Symbol Properties Database: {symbol.Value}";
+                return $"{symbol.SecurityType} '{symbol.Value}' symbol could not be found in the database for {symbol.ID.Market} market";
             }
         }
 

Tests/Api/ApiTestBase.cs

@@ -178,7 +178,13 @@ public static Backtest WaitForBacktestCompletion(Api.Api apiClient, int projectI
             {
                 Thread.Sleep(1000);
                 backtest = apiClient.ReadBacktest(projectId, backtestId);
-                if (backtest != null && (!string.IsNullOrEmpty(backtest.Error) || backtest.HasInitializeError))
+                if (backtest == null)
+                {
+                    // api failed, let's retry
+                    continue;
+                }
+
+                if (!string.IsNullOrEmpty(backtest.Error) || backtest.HasInitializeError)
                 {
                     Assert.Fail($"Backtest {projectId}/{backtestId} failed: {backtest.Error}. Stacktrace: {backtest.Stacktrace}. Api errors: {string.Join(",", backtest.Errors)}");
                 }