diff --git a/packages/utils/jest.config.js b/packages/utils/jest.config.js
index dd0f828822..fc4b6ff6d4 100644
--- a/packages/utils/jest.config.js
+++ b/packages/utils/jest.config.js
@@ -15,10 +15,10 @@ module.exports = {
   coverageReporters: ['clover', 'json', 'lcov', 'text', 'json-summary'],
   coverageThreshold: {
     global: {
-      branches: 86.05,
-      functions: 97,
-      lines: 96.68,
-      statements: 96.76,
+      branches: 85.64,
+      functions: 97.19,
+      lines: 96.63,
+      statements: 96.7,
     },
   },
   moduleFileExtensions: ['js', 'json', 'jsx', 'ts', 'tsx', 'node'],
diff --git a/packages/utils/src/types.test.ts b/packages/utils/src/types.test.ts
new file mode 100644
index 0000000000..54686a746a
--- /dev/null
+++ b/packages/utils/src/types.test.ts
@@ -0,0 +1,107 @@
+import {
+  assertIsNpmSnapPackageJson,
+  assertIsSnapManifest,
+  isNpmSnapPackageJson,
+  isSnapManifest,
+} from './types';
+import { getPackageJson, getSnapManifest } from './test-utils';
+
+describe('isNpmSnapPackageJson', () => {
+  it('returns true for a valid package.json', () => {
+    expect(isNpmSnapPackageJson(getPackageJson())).toBe(true);
+  });
+
+  it.each([
+    true,
+    false,
+    null,
+    undefined,
+    0,
+    1,
+    '',
+    'foo',
+    [],
+    {},
+    { name: 'foo' },
+    { version: '1.0.0' },
+    getPackageJson({ name: 'foo bar' }),
+  ])('returns false for an invalid package.json', (value) => {
+    expect(isNpmSnapPackageJson(value)).toBe(false);
+  });
+});
+
+describe('assertIsNpmSnapPackageJson', () => {
+  it('does not throw for a valid package.json', () => {
+    expect(() => assertIsNpmSnapPackageJson(getPackageJson())).not.toThrow();
+  });
+
+  it.each([
+    true,
+    false,
+    null,
+    undefined,
+    0,
+    1,
+    '',
+    'foo',
+    [],
+    {},
+    { name: 'foo' },
+    { version: '1.0.0' },
+    getPackageJson({ name: 'foo bar' }),
+  ])('throws for an invalid package.json', (value) => {
+    expect(() => assertIsNpmSnapPackageJson(value)).toThrow(
+      '"package.json" is invalid:',
+    );
+  });
+});
+
+describe('isSnapManifest', () => {
+  it('returns true for a valid snap manifest', () => {
+    expect(isSnapManifest(getSnapManifest())).toBe(true);
+  });
+
+  it.each([
+    true,
+    false,
+    null,
+    undefined,
+    0,
+    1,
+    '',
+    'foo',
+    [],
+    {},
+    { name: 'foo' },
+    { version: '1.0.0' },
+    getSnapManifest({ version: 'foo bar' }),
+  ])('returns false for an invalid snap manifest', (value) => {
+    expect(isSnapManifest(value)).toBe(false);
+  });
+});
+
+describe('assertIsSnapManifest', () => {
+  it('does not throw for a valid snap manifest', () => {
+    expect(() => assertIsSnapManifest(getSnapManifest())).not.toThrow();
+  });
+
+  it.each([
+    true,
+    false,
+    null,
+    undefined,
+    0,
+    1,
+    '',
+    'foo',
+    [],
+    {},
+    { name: 'foo' },
+    { version: '1.0.0' },
+    getSnapManifest({ version: 'foo bar' }),
+  ])('throws for an invalid snap manifest', (value) => {
+    expect(() => assertIsSnapManifest(value)).toThrow(
+      '"snap.manifest.json" is invalid:',
+    );
+  });
+});