Fail when there are no commands defined

CliFx.Tests/CliApplicationTests.cs

@@ -23,7 +23,7 @@ namespace CliFx.Tests
         }
 
         [Command("faulty-command")]
-        private class FaultyCommand : ICommand
+        private class TestFaultyCommand : ICommand
         {
             public Task ExecuteAsync(CommandContext context) => Task.FromException(new CommandErrorException(-1337));
         }
@@ -86,6 +86,53 @@ namespace CliFx.Tests
 
             // Default command is not defined
 
+            yield return new TestCaseData(
+                new[] {typeof(TestNamedCommand)},
+                new string[0]
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(TestNamedCommand)},
+                new[] {"--version"}
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(TestNamedCommand)},
+                new[] {"--help"}
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(TestNamedCommand)},
+                new[] {"-h"}
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(TestNamedCommand)},
+                new[] {"-?"}
+            );
+
+            // Specified a faulty command
+
+            yield return new TestCaseData(
+                new[] {typeof(TestFaultyCommand)},
+                new[] {"faulty-command", "--help"}
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(TestFaultyCommand)},
+                new[] {"faulty-command", "-h"}
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(TestFaultyCommand)},
+                new[] {"faulty-command", "-?"}
+            );
+        }
+
+        private static IEnumerable<TestCaseData> GetTestCases_RunAsync_Negative()
+        {
+            // No commands defined
+
             yield return new TestCaseData(
                 new Type[0],
                 new string[0]
@@ -111,33 +158,6 @@ namespace CliFx.Tests
                 new[] {"-?"}
             );
 
-            // Specified a faulty command
-
-            yield return new TestCaseData(
-                new[] {typeof(FaultyCommand)},
-                new[] {"--version"}
-            );
-
-            yield return new TestCaseData(
-                new[] {typeof(FaultyCommand)},
-                new[] {"--help"}
-            );
-
-            yield return new TestCaseData(
-                new[] {typeof(FaultyCommand)},
-                new[] {"-h"}
-            );
-
-            yield return new TestCaseData(
-                new[] {typeof(FaultyCommand)},
-                new[] {"-?"}
-            );
-        }
-
-        private static IEnumerable<TestCaseData> GetTestCases_RunAsync_Negative()
-        {
-            // Specified command is not defined
-
             yield return new TestCaseData(
                 new Type[0],
                 new[] {"command"}
@@ -145,23 +165,35 @@ namespace CliFx.Tests
 
             yield return new TestCaseData(
                 new Type[0],
+                new[] {"faulty-command"}
+            );
+
+            // Specified command is not defined
+
+            yield return new TestCaseData(
+                new[] {typeof(TestDefaultCommand)},
+                new[] {"command"}
+            );
+
+            yield return new TestCaseData(
+                new[] {typeof(TestDefaultCommand)},
                 new[] {"command", "--help"}
             );
 
             yield return new TestCaseData(
-                new Type[0],
+                new[] {typeof(TestDefaultCommand)},
                 new[] {"command", "-h"}
             );
 
             yield return new TestCaseData(
-                new Type[0],
+                new[] {typeof(TestDefaultCommand)},
                 new[] {"command", "-?"}
             );
 
             // Specified a faulty command
 
             yield return new TestCaseData(
-                new[] {typeof(FaultyCommand)},
+                new[] {typeof(TestFaultyCommand)},
                 new[] {"faulty-command"}
             );
         }

CliFx/CliApplication.cs

@@ -55,13 +55,26 @@ namespace CliFx
                 var availableCommandSchemas = _commandSchemaResolver.GetCommandSchemas(_commandTypes);
                 var matchingCommandSchema = availableCommandSchemas.FindByNameOrNull(commandInput.CommandName);
 
+                // Fail if there are no commands defined
+                if (!availableCommandSchemas.Any())
+                {
+                    stdErr.WriteLine("There are no commands defined in this application.");
+                    return -1;
+                }
+
                 // Fail if specified a command which is not defined
                 if (commandInput.IsCommandSpecified() && matchingCommandSchema == null)
                 {
-                    stdErr.WriteLine($"Specified command [{commandInput.CommandName}] doesn't exist.");
+                    stdErr.WriteLine($"Specified command [{commandInput.CommandName}] is not defined.");
                     return -1;
                 }
 
+                // Use a stub if command was not specified but there is no default command defined
+                if (matchingCommandSchema == null)
+                {
+                    matchingCommandSchema = _commandSchemaResolver.GetCommandSchema(typeof(StubDefaultCommand));
+                }
+
                 // Show version if it was requested without specifying a command
                 if (commandInput.IsVersionRequested() && !commandInput.IsCommandSpecified())
                 {
@@ -70,12 +83,6 @@ namespace CliFx
                     return 0;
                 }
 
-                // Use a stub if command was not specified but there is no default command defined
-                if (matchingCommandSchema == null)
-                {
-                    matchingCommandSchema = _commandSchemaResolver.GetCommandSchema(typeof(StubDefaultCommand));
-                }
-
                 // Show help if it was requested
                 if (commandInput.IsHelpRequested())
                 {