[flutter_tools] Remove mocking and simplify Dart target tests (#50688)

packages/flutter_tools/lib/src/compile.dart

@@ -241,7 +241,8 @@ class PackageUriMapper {
   }
 }
 
-List<String> _buildModeOptions(BuildMode mode) {
+/// List the preconfigured build options for a given build mode.
+List<String> buildModeOptions(BuildMode mode) {
   switch (mode) {
     case BuildMode.debug:
       return <String>[
@@ -316,7 +317,7 @@ class KernelCompiler {
       '-Ddart.developer.causal_async_stacks=${buildMode == BuildMode.debug}',
       for (final Object dartDefine in dartDefines)
         '-D$dartDefine',
-      ..._buildModeOptions(buildMode),
+      ...buildModeOptions(buildMode),
       if (trackWidgetCreation) '--track-widget-creation',
       if (!linkPlatformKernelIn) '--no-link-platform',
       if (aot) ...<String>[
@@ -357,14 +358,9 @@ class KernelCompiler {
     ];
 
     globals.printTrace(command.join(' '));
-    final Process server = await globals.processManager
-      .start(command)
-      .catchError((dynamic error, StackTrace stack) {
-        globals.printError('Failed to start frontend server $error, $stack');
-      });
+    final Process server = await globals.processManager.start(command);
 
     final StdoutHandler _stdoutHandler = StdoutHandler();
-
     server.stderr
       .transform<String>(utf8.decoder)
       .listen(globals.printError);
@@ -678,7 +674,7 @@ class DefaultResidentCompiler implements ResidentCompiler {
         '--packages',
         packagesPath,
       ],
-      ..._buildModeOptions(buildMode),
+      ...buildModeOptions(buildMode),
       if (trackWidgetCreation) '--track-widget-creation',
       if (fileSystemRoots != null)
         for (final String root in fileSystemRoots) ...<String>[

packages/flutter_tools/test/src/fake_process_manager.dart

@@ -202,6 +202,11 @@ abstract class FakeProcessManager implements ProcessManager {
   /// This is a no-op on [FakeProcessManager.any].
   void addCommand(FakeCommand command);
 
+  /// Whether this fake has more [FakeCommand]s that are expected to run.
+  ///
+  /// This is always `true` for [FakeProcessManager.any].
+  bool get hasRemainingExpectations;
+
   @protected
   FakeCommand findCommand(List<String> command, String workingDirectory, Map<String, String> environment);
 
@@ -299,6 +304,9 @@ class _FakeAnyProcessManager extends FakeProcessManager {
 
   @override
   void addCommand(FakeCommand command) { }
+
+  @override
+  bool get hasRemainingExpectations => true;
 }
 
 class _SequenceProcessManager extends FakeProcessManager {
@@ -325,4 +333,7 @@ class _SequenceProcessManager extends FakeProcessManager {
   void addCommand(FakeCommand command) {
     _commands.add(command);
   }
+
+  @override
+  bool get hasRemainingExpectations => _commands.isNotEmpty;
 }