diff --git a/packages/type-utils/tests/isTypeReadonly.test.ts b/packages/type-utils/tests/isTypeReadonly.test.ts
new file mode 100644
index 000000000000..7153b44d7769
--- /dev/null
+++ b/packages/type-utils/tests/isTypeReadonly.test.ts
@@ -0,0 +1,219 @@
+import * as ts from 'typescript';
+import { TSESTree } from '@typescript-eslint/experimental-utils';
+import { parseForESLint } from '@typescript-eslint/parser';
+import {
+  isTypeReadonly,
+  type ReadonlynessOptions,
+} from '../src/isTypeReadonly';
+import path from 'path';
+
+describe('isTypeReadonly', () => {
+  const rootDir = path.join(__dirname, 'fixtures');
+
+  describe('TSTypeAliasDeclaration ', () => {
+    function getType(code: string): {
+      type: ts.Type;
+      checker: ts.TypeChecker;
+    } {
+      const { ast, services } = parseForESLint(code, {
+        project: './tsconfig.json',
+        filePath: path.join(rootDir, 'file.ts'),
+        tsconfigRootDir: rootDir,
+      });
+      const checker = services.program.getTypeChecker();
+      const esTreeNodeToTSNodeMap = services.esTreeNodeToTSNodeMap;
+
+      const declaration = ast.body[0] as TSESTree.TSTypeAliasDeclaration;
+      return {
+        type: checker.getTypeAtLocation(
+          esTreeNodeToTSNodeMap.get(declaration.id),
+        ),
+        checker,
+      };
+    }
+
+    describe('basics', () => {
+      describe('is readonly', () => {
+        describe('default options', () => {
+          it('handles a record with only readonly props', () => {
+            const { type, checker } = getType(
+              `type Test = { readonly bar: string; };`,
+            );
+
+            const result = isTypeReadonly(checker, type);
+            expect(result).toBe(true);
+          });
+
+          it('handles a shallowly mutable record wrapped in Readonly', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = Readonly<{ bar: string; }>;`,
+            );
+
+            const result = isTypeReadonly(checker, receiver);
+            expect(result).toBe(true);
+          });
+
+          it('handles an readonly readonly array', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = Readonly<readonly string[]>;`,
+            );
+
+            const result = isTypeReadonly(checker, receiver);
+            expect(result).toBe(true);
+          });
+
+          it('handles an readonly ReadonlyArray', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = Readonly<ReadonlyArray<string>>;`,
+            );
+
+            const result = isTypeReadonly(checker, receiver);
+            expect(result).toBe(true);
+          });
+
+          it('handles an readonly ReadonlySet', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = Readonly<ReadonlySet<string>>;`,
+            );
+
+            const result = isTypeReadonly(checker, receiver);
+            expect(result).toBe(true);
+          });
+
+          // Methods are mutable but arrays have a special exemption; hence no failure.
+          it('handles a readonly array', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = readonly string[];`,
+            );
+
+            const result = isTypeReadonly(checker, receiver);
+            expect(result).toBe(true);
+          });
+
+          // Methods are mutable but arrays have a special exemption; hence no failure.
+          it('handles a ReadonlyArray', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = ReadonlyArray<string>;`,
+            );
+
+            const result = isTypeReadonly(checker, receiver);
+            expect(result).toBe(true);
+          });
+        });
+
+        describe('treatMethodsAsReadonly', () => {
+          const options: ReadonlynessOptions = {
+            treatMethodsAsReadonly: true,
+          };
+
+          it('handles a ReadonlySet', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = ReadonlySet<string>;`,
+            );
+
+            const result = isTypeReadonly(checker, receiver, options);
+            expect(result).toBe(true);
+          });
+
+          it('handles a ReadonlyMap', () => {
+            const { type: receiver, checker } = getType(
+              `type Test = ReadonlyMap<string, string>;`,
+            );
+
+            const result = isTypeReadonly(checker, receiver, options);
+            expect(result).toBe(true);
+          });
+        });
+      });
+
+      describe('is not readonly', () => {
+        it('fails with record with mutable props', () => {
+          const { type: receiver, checker } = getType(
+            `type Test = { bar: string; };`,
+          );
+
+          const result = isTypeReadonly(checker, receiver);
+          expect(result).toBe(false);
+        });
+
+        it('fails with a mutable array', () => {
+          const { type: receiver, checker } = getType(`type Test = string[];`);
+
+          const result = isTypeReadonly(checker, receiver);
+          expect(result).toBe(false);
+        });
+
+        it('fails with a mutable Array', () => {
+          const { type: receiver, checker } = getType(
+            `type Test = Array<string>;`,
+          );
+
+          const result = isTypeReadonly(checker, receiver);
+          expect(result).toBe(false);
+        });
+
+        // Methods are mutable; hence failure.
+        it('fails with a ReadonlySet', () => {
+          const { type: receiver, checker } = getType(
+            `type Test = ReadonlySet<string>;`,
+          );
+
+          const result = isTypeReadonly(checker, receiver);
+          expect(result).toBe(false);
+        });
+
+        // Methods are mutable; hence failure.
+        it('fails with a ReadonlyMap', () => {
+          const { type: receiver, checker } = getType(
+            `type Test = ReadonlyMap<string, string>;`,
+          );
+
+          const result = isTypeReadonly(checker, receiver);
+          expect(result).toBe(false);
+        });
+      });
+    });
+
+    describe('Intersection', () => {
+      describe('is readonly', () => {
+        it('handles an intersection of 2', () => {
+          const { type, checker } = getType(
+            `type Test = Readonly<{ foo: string; bar: number; }> & Readonly<{ bar: number; }>;`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(true);
+        });
+      });
+
+      describe('is not readonly', () => {
+        it('fails with an intersection of mutables', () => {
+          const { type, checker } = getType(
+            `type Test = { foo: string; bar: number; } & { bar: number; };`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(false);
+        });
+
+        it('fails with an intersection of mutable to readonly', () => {
+          const { type, checker } = getType(
+            `type Test = { foo: string; bar: number; } & Readonly<{ bar: number; }>;`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(false);
+        });
+
+        it('fails with an intersection of readonly to mutable', () => {
+          const { type, checker } = getType(
+            `type Test = { foo: string; bar: number; } & Readonly<{ bar: number; }>;`,
+          );
+
+          const result = isTypeReadonly(checker, type);
+          expect(result).toBe(false);
+        });
+      });
+    });
+  });
+});