diff --git a/tools/engine_tool/BUILD.gn b/tools/engine_tool/BUILD.gn
index 0f66898cfc520..0171d080b2fae 100644
--- a/tools/engine_tool/BUILD.gn
+++ b/tools/engine_tool/BUILD.gn
@@ -37,7 +37,7 @@ dart_test("gn_test") {
 }
 
 dart_test("build_command_test") {
-  main_dart = "test/build_command_test.dart"
+  main_dart = "test/commands/build_command_test.dart"
 }
 
 dart_test("entry_point_test") {
@@ -45,11 +45,11 @@ dart_test("entry_point_test") {
 }
 
 dart_test("fetch_command_test") {
-  main_dart = "test/fetch_command_test.dart"
+  main_dart = "test/commands/fetch_command_test.dart"
 }
 
 dart_test("format_command_test") {
-  main_dart = "test/format_command_test.dart"
+  main_dart = "test/commands/format_command_test.dart"
 }
 
 dart_test("label_test") {
@@ -57,7 +57,7 @@ dart_test("label_test") {
 }
 
 dart_test("lint_command_test") {
-  main_dart = "test/lint_command_test.dart"
+  main_dart = "test/commands/lint_command_test.dart"
 }
 
 dart_test("logger_test") {
@@ -73,11 +73,11 @@ dart_test("proc_utils_test") {
 }
 
 dart_test("query_command_test") {
-  main_dart = "test/query_command_test.dart"
+  main_dart = "test/commands/query_command_test.dart"
 }
 
 dart_test("run_command_test") {
-  main_dart = "test/run_command_test.dart"
+  main_dart = "test/commands/run_command_test.dart"
 }
 
 dart_test("run_target_test") {
@@ -85,7 +85,7 @@ dart_test("run_target_test") {
 }
 
 dart_test("test_command_test") {
-  main_dart = "test/test_command_test.dart"
+  main_dart = "test/commands/test_command_test.dart"
 }
 
 dart_test("typed_json_test") {
diff --git a/tools/engine_tool/test/build_plan_test.dart b/tools/engine_tool/test/build_plan_test.dart
index d5b55f555800f..529641fa2d8e4 100644
--- a/tools/engine_tool/test/build_plan_test.dart
+++ b/tools/engine_tool/test/build_plan_test.dart
@@ -9,7 +9,7 @@ import 'package:engine_tool/src/logger.dart';
 import 'package:test/test.dart';
 
 import 'src/test_build_configs.dart';
-import 'utils.dart';
+import 'src/utils.dart';
 
 void main() {
   test('rbe defaults to true if detected', () {
diff --git a/tools/engine_tool/test/build_command_test.dart b/tools/engine_tool/test/commands/build_command_test.dart
similarity index 95%
rename from tools/engine_tool/test/build_command_test.dart
rename to tools/engine_tool/test/commands/build_command_test.dart
index 12401b95bde13..615b16943e2bc 100644
--- a/tools/engine_tool/test/build_command_test.dart
+++ b/tools/engine_tool/test/commands/build_command_test.dart
@@ -5,16 +5,14 @@
 import 'dart:convert' as convert;
 import 'dart:ffi';
 
-import 'package:engine_build_configs/engine_build_configs.dart';
 import 'package:engine_tool/src/build_utils.dart';
 import 'package:engine_tool/src/commands/command_runner.dart';
 import 'package:engine_tool/src/logger.dart';
 import 'package:path/path.dart' as path;
 import 'package:test/test.dart';
 
-import 'fixtures.dart' as fixtures;
-import 'src/test_build_configs.dart';
-import 'utils.dart';
+import '../src/test_build_configs.dart';
+import '../src/utils.dart';
 
 void main() {
   test('can find host runnable build', () async {
@@ -401,20 +399,28 @@ void main() {
 
   test('local config name on the command line is correctly translated',
       () async {
-    final namespaceTestConfigs = BuilderConfig.fromJson(
-      path: 'ci/builders/namespace_test_config.json',
-      map: convert.jsonDecode(fixtures.configsToTestNamespacing)
-          as Map<String, Object?>,
+    final builder = TestBuilderConfig();
+    builder.addBuild(
+      name: 'linux/host_debug',
+      dimension: TestDroneDimension.linux,
+      targetDir: 'local_host_debug',
     );
-    final configs = <String, BuilderConfig>{
-      'namespace_test_config': namespaceTestConfigs,
-    };
+    builder.addBuild(
+      name: 'ci/host_debug',
+      dimension: TestDroneDimension.linux,
+      targetDir: 'ci/host_debug',
+    );
+
     final testEnv = TestEnvironment.withTestEngine();
     addTearDown(testEnv.cleanup);
 
     final runner = ToolCommandRunner(
       environment: testEnv.environment,
-      configs: configs,
+      configs: {
+        'namespace_test_config': builder.buildConfig(
+          path: 'ci/builders/namespace_test_config.json',
+        ),
+      },
     );
     final result = await runner.run([
       'build',
@@ -428,20 +434,27 @@ void main() {
   });
 
   test('ci config name on the command line is correctly translated', () async {
-    final namespaceTestConfigs = BuilderConfig.fromJson(
-      path: 'ci/builders/namespace_test_config.json',
-      map: convert.jsonDecode(fixtures.configsToTestNamespacing)
-          as Map<String, Object?>,
+    final builder = TestBuilderConfig();
+    builder.addBuild(
+      name: 'linux/host_debug',
+      dimension: TestDroneDimension.linux,
+      targetDir: 'local_host_debug',
+    );
+    builder.addBuild(
+      name: 'ci/host_debug',
+      dimension: TestDroneDimension.linux,
+      targetDir: 'ci/host_debug',
     );
-    final configs = <String, BuilderConfig>{
-      'namespace_test_config': namespaceTestConfigs,
-    };
     final testEnv = TestEnvironment.withTestEngine();
     addTearDown(testEnv.cleanup);
 
     final runner = ToolCommandRunner(
       environment: testEnv.environment,
-      configs: configs,
+      configs: {
+        'namespace_test_config': builder.buildConfig(
+          path: 'ci/builders/namespace_test_config.json',
+        ),
+      },
     );
     final result = await runner.run([
       'build',
diff --git a/tools/engine_tool/test/fetch_command_test.dart b/tools/engine_tool/test/commands/fetch_command_test.dart
similarity index 100%
rename from tools/engine_tool/test/fetch_command_test.dart
rename to tools/engine_tool/test/commands/fetch_command_test.dart
diff --git a/tools/engine_tool/test/format_command_test.dart b/tools/engine_tool/test/commands/format_command_test.dart
similarity index 100%
rename from tools/engine_tool/test/format_command_test.dart
rename to tools/engine_tool/test/commands/format_command_test.dart
diff --git a/tools/engine_tool/test/lint_command_test.dart b/tools/engine_tool/test/commands/lint_command_test.dart
similarity index 100%
rename from tools/engine_tool/test/lint_command_test.dart
rename to tools/engine_tool/test/commands/lint_command_test.dart
diff --git a/tools/engine_tool/test/query_command_test.dart b/tools/engine_tool/test/commands/query_command_test.dart
similarity index 99%
rename from tools/engine_tool/test/query_command_test.dart
rename to tools/engine_tool/test/commands/query_command_test.dart
index 4599a68bfeaf7..77edae6f36864 100644
--- a/tools/engine_tool/test/query_command_test.dart
+++ b/tools/engine_tool/test/commands/query_command_test.dart
@@ -9,8 +9,8 @@ import 'package:engine_tool/src/commands/command_runner.dart';
 import 'package:logging/logging.dart' as log;
 import 'package:test/test.dart';
 
-import 'src/test_build_configs.dart';
-import 'utils.dart';
+import '../src/test_build_configs.dart';
+import '../src/utils.dart';
 
 void main() {
   List<String> stringsFromLogs(List<log.LogRecord> logs) {
diff --git a/tools/engine_tool/test/test_command_test.dart b/tools/engine_tool/test/commands/test_command_test.dart
similarity index 98%
rename from tools/engine_tool/test/test_command_test.dart
rename to tools/engine_tool/test/commands/test_command_test.dart
index 84ebc58eeb130..505f920adfbab 100644
--- a/tools/engine_tool/test/test_command_test.dart
+++ b/tools/engine_tool/test/commands/test_command_test.dart
@@ -5,8 +5,8 @@
 import 'package:engine_tool/src/commands/command_runner.dart';
 import 'package:test/test.dart';
 
-import 'src/test_build_configs.dart';
-import 'utils.dart';
+import '../src/test_build_configs.dart';
+import '../src/utils.dart';
 
 void main() {
   test('test implicitly picks a configuration and executes tests', () async {
diff --git a/tools/engine_tool/test/external_tools/flutter_tools_test.dart b/tools/engine_tool/test/external_tools/flutter_tools_test.dart
index 4a080038b7716..61ef86e01edfb 100644
--- a/tools/engine_tool/test/external_tools/flutter_tools_test.dart
+++ b/tools/engine_tool/test/external_tools/flutter_tools_test.dart
@@ -11,7 +11,7 @@ import 'package:engine_tool/src/logger.dart';
 import 'package:test/test.dart';
 
 import '../src/matchers.dart';
-import '../utils.dart';
+import '../src/utils.dart';
 
 void main() {
   test('devices handles a non-zero exit code', () async {
diff --git a/tools/engine_tool/test/external_tools/gn_test.dart b/tools/engine_tool/test/external_tools/gn_test.dart
index efd1a8c463ffd..b3e866816db3b 100644
--- a/tools/engine_tool/test/external_tools/gn_test.dart
+++ b/tools/engine_tool/test/external_tools/gn_test.dart
@@ -7,7 +7,7 @@ import 'package:engine_tool/src/label.dart';
 import 'package:engine_tool/src/logger.dart';
 import 'package:test/test.dart';
 
-import '../utils.dart';
+import '../src/utils.dart';
 
 void main() {
   test('gn.desc handles a non-zero exit code', () async {
diff --git a/tools/engine_tool/test/fixtures.dart b/tools/engine_tool/test/fixtures.dart
deleted file mode 100644
index 42d7f24d95def..0000000000000
--- a/tools/engine_tool/test/fixtures.dart
+++ /dev/null
@@ -1,228 +0,0 @@
-// Copyright 2013 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-String testConfig(String osDimension, String osPlatform,
-        {String suffix = ''}) =>
-    '''
-{
-  "builds": [
-    {
-      "archives": [
-        {
-          "name": "build_name$suffix",
-          "base_path": "base/path",
-          "type": "gcs",
-          "include_paths": ["include/path"],
-          "realm": "archive_realm"
-        }
-      ],
-      "drone_dimensions": [
-        "os=$osDimension"
-      ],
-      "gclient_variables": {
-        "variable": false
-      },
-      "gn": ["--gn-arg", "--lto", "--no-rbe"],
-      "name": "ci/build_name$suffix",
-      "description": "This is a very long description that will test that the help message is wrapped correctly at an appropriate number of characters.",
-      "ninja": {
-        "config": "build_name$suffix",
-        "targets": ["ninja_target"]
-      },
-      "tests": [
-        {
-          "language": "python3",
-          "name": "build_name$suffix tests",
-          "parameters": ["--test-params"],
-          "script": "test/script.py",
-          "contexts": ["context"]
-        }
-      ],
-      "generators": {
-        "tasks": [
-          {
-            "name": "generator_task",
-            "language": "python",
-            "parameters": ["--gen-param"],
-            "scripts": ["gen/script.py"]
-          }
-        ]
-      }
-    },
-    {},
-    {},
-    {
-      "drone_dimensions": [
-        "os=$osDimension"
-      ],
-      "gn": ["--gn-arg", "--lto", "--no-rbe"],
-      "name": "$osPlatform/host_debug$suffix",
-      "ninja": {
-        "config": "host_debug$suffix",
-        "targets": ["ninja_target"]
-      }
-    },
-    {
-      "drone_dimensions": [
-        "os=$osDimension"
-      ],
-      "gn": ["--gn-arg", "--lto", "--no-rbe"],
-      "name": "$osPlatform/android_debug${suffix}_arm64",
-      "ninja": {
-        "config": "android_debug${suffix}_arm64",
-        "targets": ["ninja_target"]
-      }
-    },
-    {
-      "drone_dimensions": [
-        "os=$osDimension"
-      ],
-      "gn": ["--gn-arg", "--lto", "--rbe"],
-      "name": "ci/android_debug${suffix}_rbe_arm64",
-      "ninja": {
-        "config": "android_debug${suffix}_rbe_arm64",
-        "targets": ["ninja_target"]
-      }
-    }
-  ],
-  "generators": {
-    "tasks": [
-      {
-        "name": "global generator task",
-        "parameters": ["--global-gen-param"],
-        "script": "global/gen_script.dart",
-        "language": "dart"
-      }
-    ]
-  },
-  "tests": [
-    {
-      "name": "global test",
-      "recipe": "engine_v2/tester_engine",
-      "drone_dimensions": [
-        "os=$osDimension"
-      ],
-      "gclient_variables": {
-        "variable": false
-      },
-      "dependencies": ["dependency"],
-      "test_dependencies": [
-        {
-          "dependency": "test_dependency",
-          "version": "git_revision:3a77d0b12c697a840ca0c7705208e8622dc94603"
-        }
-      ],
-      "tasks": [
-        {
-          "name": "global test task",
-          "parameters": ["--test-parameter"],
-          "script": "global/test/script.py"
-        }
-      ]
-    }
-  ]
-}
-''';
-
-const String configsToTestNamespacing = '''
-{
-  "builds": [
-    {
-      "drone_dimensions": [
-        "os=Linux"
-      ],
-      "gn": ["--gn-arg", "--lto", "--no-rbe"],
-      "name": "linux/host_debug",
-      "ninja": {
-        "config": "local_host_debug",
-        "targets": ["ninja_target"]
-      }
-    },
-    {
-      "drone_dimensions": [
-        "os=Linux"
-      ],
-      "gn": ["--gn-arg", "--lto", "--no-rbe"],
-      "name": "ci/host_debug",
-      "ninja": {
-        "config": "ci/host_debug",
-        "targets": ["ninja_target"]
-      }
-    }
-  ]
-}
-''';
-
-String attachedDevices() => '''
-[
-  {
-    "name": "sdk gphone64 arm64",
-    "id": "emulator-5554",
-    "isSupported": true,
-    "targetPlatform": "android-arm64",
-    "emulator": true,
-    "sdk": "Android 14 (API 34)",
-    "capabilities": {
-      "hotReload": true,
-      "hotRestart": true,
-      "screenshot": true,
-      "fastStart": true,
-      "flutterExit": true,
-      "hardwareRendering": true,
-      "startPaused": true
-    }
-  },
-  {
-    "name": "macOS",
-    "id": "macos",
-    "isSupported": true,
-    "targetPlatform": "darwin",
-    "emulator": false,
-    "sdk": "macOS 14.3.1 23D60 darwin-arm64",
-    "capabilities": {
-      "hotReload": true,
-      "hotRestart": true,
-      "screenshot": false,
-      "fastStart": false,
-      "flutterExit": true,
-      "hardwareRendering": false,
-      "startPaused": true
-    }
-  },
-  {
-    "name": "Mac Designed for iPad",
-    "id": "mac-designed-for-ipad",
-    "isSupported": true,
-    "targetPlatform": "darwin",
-    "emulator": false,
-    "sdk": "macOS 14.3.1 23D60 darwin-arm64",
-    "capabilities": {
-      "hotReload": true,
-      "hotRestart": true,
-      "screenshot": false,
-      "fastStart": false,
-      "flutterExit": true,
-      "hardwareRendering": false,
-      "startPaused": true
-    }
-  },
-  {
-    "name": "Chrome",
-    "id": "chrome",
-    "isSupported": true,
-    "targetPlatform": "web-javascript",
-    "emulator": false,
-    "sdk": "Google Chrome 122.0.6261.94",
-    "capabilities": {
-      "hotReload": true,
-      "hotRestart": true,
-      "screenshot": false,
-      "fastStart": false,
-      "flutterExit": false,
-      "hardwareRendering": false,
-      "startPaused": true
-    }
-  }
-]
-''';
diff --git a/tools/engine_tool/test/utils.dart b/tools/engine_tool/test/src/utils.dart
similarity index 100%
rename from tools/engine_tool/test/utils.dart
rename to tools/engine_tool/test/src/utils.dart
diff --git a/tools/engine_tool/test/utils_test.dart b/tools/engine_tool/test/utils_test.dart
index 84bae34edbd4f..1efbba989801f 100644
--- a/tools/engine_tool/test/utils_test.dart
+++ b/tools/engine_tool/test/utils_test.dart
@@ -4,7 +4,7 @@
 
 import 'package:test/test.dart';
 
-import 'utils.dart';
+import 'src/utils.dart';
 
 void main() async {
   final cannedProcesses = <CannedProcess>[