Use minimum package versions in tests too (#816)

diff --git a/lib/src/project_creator.dart b/lib/src/project_creator.dart
index 1674142..0c097ff 100644
--- a/lib/src/project_creator.dart
+++ b/lib/src/project_creator.dart
@@ -141,10 +141,20 @@
         parsePubDependenciesFile(dependenciesFile: _dependenciesFile);
     return {
       for (var package in packages) package: allVersions[package] ?? 'any',
+      // Overwrite with important constraints:
+      ...packageVersionConstraints,
     };
   }
 }
 
+/// A mapping of version constraints for certain packages.
+const packageVersionConstraints = {
+  // Ensure that pub version solving keeps these at sane minimum versions.
+  'cloud_firestore': '^3.1.0',
+  'firebase_auth': '^3.3.0',
+  'firebase_core': '^1.10.0',
+};
+
 /// Parses [dependenciesFile] as a JSON Map of Strings.
 Map<String, String> parsePubDependenciesFile({required File dependenciesFile}) {
   final packageVersions =
diff --git a/tool/grind.dart b/tool/grind.dart
index e4f5461..e830f38 100644
--- a/tool/grind.dart
+++ b/tool/grind.dart
@@ -413,7 +413,7 @@
       for (var package in supportedFlutterPackages) package: 'any',
       for (var package in supportedBasicDartPackages) package: 'any',
       // Overwrite with important constraints:
-      ..._packageVersionConstraints,
+      ...packageVersionConstraints,
     },
   );
   joinFile(tempDir, ['pubspec.yaml']).writeAsStringSync(pubspec);
@@ -424,14 +424,6 @@
       .writeAsStringSync(_jsonEncoder.convert(packageVersions));
 }
 
-/// A mapping of version constraints for certain packages.
-const _packageVersionConstraints = {
-  // Ensure that pub version solving keeps these at sane minimum versions.
-  'cloud_firestore': '^3.1.0',
-  'firebase_auth': '^3.3.0',
-  'firebase_core': '^1.10.0',
-};
-
 /// An encoder which indents nested elements by two spaces.
 const JsonEncoder _jsonEncoder = JsonEncoder.withIndent('  ');