add dep overrides for test items

Author: kevmoo

pubspec.yaml

@@ -16,3 +16,61 @@ dev_dependencies:
   build_runner: ^1.0.0
   build_test: ^0.10.0
   build_web_compilers: '>=1.2.0 <3.0.0'
+
+dependency_overrides:
+  async:
+    git:
+      url: git://github.com/dart-lang/async.git
+      ref: null_safety
+  boolean_selector:
+    git:
+      url: git://github.com/dart-lang/boolean_selector.git
+      ref: null_safety
+  charcode:
+    git:
+      url: git://github.com/dart-lang/charcode.git
+      ref: null_safety
+  collection:
+    git:
+      url: git://github.com/dart-lang/collection.git
+      ref: null_safety
+  matcher:
+    git:
+      url: git://github.com/dart-lang/matcher.git
+      ref: null_safety
+  meta:
+    git:
+      url: git://github.com/dart-lang/sdk.git
+      ref: null_safety-pkgs
+      path: pkg/meta
+  path:
+    git:
+      url: git://github.com/dart-lang/path.git
+      ref: null_safety
+  source_span:
+    git:
+      url: git://github.com/dart-lang/source_span.git
+      ref: null_safety
+  stack_trace:
+    git:
+      url: git://github.com/dart-lang/stack_trace.git
+      ref: null_safety
+  term_glyph:
+    git:
+      url: git://github.com/dart-lang/term_glyph.git
+      ref: null_safety
+  test_api:
+    git:
+      url: git://github.com/dart-lang/test.git
+      ref: null_safety
+      path: pkgs/test_api
+  test_core:
+    git:
+      url: git://github.com/dart-lang/test.git
+      ref: null_safety
+      path: pkgs/test_core
+  test:
+    git:
+      url: git://github.com/dart-lang/test.git
+      ref: null_safety
+      path: pkgs/test