diff --git a/packages/yarn-plugin/src/resolvers/BackstageNpmResolver.test.ts b/packages/yarn-plugin/src/resolvers/BackstageNpmResolver.test.ts
new file mode 100644
index 0000000000..46621fe12b
--- /dev/null
+++ b/packages/yarn-plugin/src/resolvers/BackstageNpmResolver.test.ts
@@ -0,0 +1,167 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import { ResolveOptions, structUtils } from '@yarnpkg/core';
+import { BackstageNpmResolver } from './BackstageNpmResolver';
+import { NpmSemverResolver } from '@yarnpkg/plugin-npm';
+
+const mockGetCandidates = jest.fn();
+const mockGetSatisfying = jest.fn();
+jest.mock('@yarnpkg/plugin-npm', () => {
+  return {
+    ...jest.requireActual('@yarnpkg/plugin-npm'),
+    NpmSemverResolver: function MockNpmSemverResolver() {
+      return {
+        getCandidates: mockGetCandidates,
+        getSatisfying: mockGetSatisfying,
+      };
+    } as unknown as NpmSemverResolver,
+  };
+});
+
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+describe('BackstageNpmResolver', () => {
+  const ident = structUtils.makeIdent('backstage', 'core');
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('getCandidates', () => {
+    it('should throw an error if the npm param is missing from the descriptor', async () => {
+      const resolver = new BackstageNpmResolver();
+
+      const descriptor = structUtils.bindDescriptor(
+        structUtils.makeDescriptor(ident, 'backstage:^'),
+        { backstage: '1.0.0' },
+      );
+
+      await expect(
+        resolver.getCandidates(descriptor, undefined!, undefined!),
+      ).rejects.toThrow(/Missing npm parameter/);
+    });
+
+    it('should call the npm resolver with the correct descriptor', async () => {
+      const resolver = new BackstageNpmResolver();
+
+      mockGetCandidates.mockResolvedValue([
+        structUtils.makeLocator(ident, '1.2.5'),
+        structUtils.makeLocator(ident, '1.2.4'),
+        structUtils.makeLocator(ident, '1.2.3'),
+      ]);
+
+      const descriptor = structUtils.bindDescriptor(
+        structUtils.makeDescriptor(ident, 'backstage:^'),
+        { backstage: '1.0.0', npm: '1.2.3' },
+      );
+
+      const deps = {};
+      const opts = {};
+
+      await expect(
+        resolver.getCandidates(descriptor, deps, opts as ResolveOptions),
+      ).resolves.toEqual([
+        structUtils.makeLocator(ident, '1.2.5'),
+        structUtils.makeLocator(ident, '1.2.4'),
+        structUtils.makeLocator(ident, '1.2.3'),
+      ]);
+
+      expect(mockGetCandidates).toHaveBeenCalledWith(
+        structUtils.makeDescriptor(descriptor, 'npm:^1.2.3'),
+        deps,
+        opts,
+      );
+    });
+  });
+
+  describe('getResolutionDependencies', () => {
+    it('should return the correct resolution dependencies', () => {
+      const resolver = new BackstageNpmResolver();
+
+      const descriptor = structUtils.bindDescriptor(
+        structUtils.makeDescriptor(ident, 'backstage:^'),
+        { backstage: '1.0.0', npm: '1.2.3' },
+      );
+
+      expect(resolver.getResolutionDependencies(descriptor)).toEqual({
+        '@backstage/core': {
+          descriptorHash: expect.any(String),
+          identHash: descriptor.identHash,
+          name: 'core',
+          range: 'npm:^1.2.3',
+          scope: 'backstage',
+        },
+      });
+    });
+  });
+
+  describe('getSatisfying', () => {
+    it('should return the correct satisfying locator', async () => {
+      const resolver = new BackstageNpmResolver();
+
+      mockGetSatisfying.mockResolvedValue({
+        locators: [
+          structUtils.makeLocator(ident, '1.2.5'),
+          structUtils.makeLocator(ident, '1.2.4'),
+          structUtils.makeLocator(ident, '1.2.3'),
+        ],
+        sorted: false,
+      });
+
+      const descriptor = structUtils.bindDescriptor(
+        structUtils.makeDescriptor(ident, 'backstage:^'),
+        { backstage: '1.0.0', npm: '1.2.3' },
+      );
+
+      await expect(
+        resolver.getSatisfying(descriptor, {}, [], {} as ResolveOptions),
+      ).resolves.toEqual({
+        locators: [
+          structUtils.makeLocator(ident, '1.2.5'),
+          structUtils.makeLocator(ident, '1.2.4'),
+          structUtils.makeLocator(ident, '1.2.3'),
+        ],
+        sorted: false,
+      });
+
+      expect(mockGetSatisfying).toHaveBeenCalledWith(
+        {
+          descriptorHash: expect.any(String),
+          identHash: ident.identHash,
+          name: 'core',
+          range: 'npm:^1.2.3',
+          scope: 'backstage',
+        },
+        {},
+        [],
+        {} as ResolveOptions,
+      );
+    });
+  });
+});