From 99ffa2aafcea475c2bbb3e3d97ac5426d88eed1c Mon Sep 17 00:00:00 2001
From: Victor Widell <victor@topmost.se>
Date: Mon, 5 Jul 2021 18:15:53 +0200
Subject: [PATCH 1/3] Made array arguments `readonly`.

The array arguments have no business being mutable.
---
 src/lib/assertion/expect.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/lib/assertion/expect.ts b/src/lib/assertion/expect.ts
index 9985531..8920ac8 100644
--- a/src/lib/assertion/expect.ts
+++ b/src/lib/assertion/expect.ts
@@ -43,7 +43,7 @@ class Expect {
    * @param expected Expected array.
    * @param message Custom assertion failure message.
    */
-  public arraysToBeEqual<T extends unknown[]>(actual: T, expected: T, message?: string) {
+  public arraysToBeEqual<T extends readonly unknown[]>(actual: T, expected: T, message?: string) {
     if (actual.length !== expected.length)
       throw new ExpectationError(message || `Expected sequences to be equal, but their lenghts were different.`);
 
@@ -219,7 +219,7 @@ class Expect {
    * @param array Array in which the given item is expected to be.
    * @param message Custom assertion failure message.
    */
-  public toBeIn<T>(item: T, array: T[], message?: string) {
+  public toBeIn<T>(item: T, array: readonly T[], message?: string) {
     const isIn = array.find((x) => x === item);
     if (this.notFlag ? isIn : !isIn) {
       throw new ExpectationError(

From 2c0ad19b0ecfb83f9ff08be3e4bd7db252c4bdaf Mon Sep 17 00:00:00 2001
From: Victor Widell <victor@topmost.se>
Date: Sun, 11 Jul 2021 19:30:15 +0200
Subject: [PATCH 2/3] Added test for ReadonlyArray.

---
 src/spec/assertion/arraysToBeEqual.spec.ts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/spec/assertion/arraysToBeEqual.spec.ts b/src/spec/assertion/arraysToBeEqual.spec.ts
index 2801324..866a537 100644
--- a/src/spec/assertion/arraysToBeEqual.spec.ts
+++ b/src/spec/assertion/arraysToBeEqual.spec.ts
@@ -10,6 +10,13 @@ export class ExpectArraysToBeEqualTestSuite {
   private equal(actual, expected) {
     expect.arraysToBeEqual(actual, expected);
   }
+  
+  @Test('ReadonlyArrays to be equal')
+  private equal() {
+    const actual: ReaonlyArray<string> = ['a', 'b', 'c'];
+    const expected: ReaonlyArray<string> = ['a', 'b', 'c'];
+    expect.arraysToBeEqual(actual, expected);
+  }  
 
   @Test('Arrays to be equal, should fail')
   @TestCase(`'a, b, c' to equal 'b, c, a'`, ['a', 'b', 'c'], ['b', 'c', 'a'])

From 1899b243278b22f34b7dfd1392540b6f499f65db Mon Sep 17 00:00:00 2001
From: Victor Widell <victor@topmost.se>
Date: Sun, 11 Jul 2021 19:33:12 +0200
Subject: [PATCH 3/3] Added test for ReadonlyArray.

---
 src/spec/assertion/toBeIn.spec.ts | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/spec/assertion/toBeIn.spec.ts b/src/spec/assertion/toBeIn.spec.ts
index 24c712b..8202198 100644
--- a/src/spec/assertion/toBeIn.spec.ts
+++ b/src/spec/assertion/toBeIn.spec.ts
@@ -7,6 +7,12 @@ export class ExpectToMatch {
   private aToBeInSuccess() {
     expect.toBeIn('a', ['a', 'b', 'c']);
   }
+  
+  @Test(`'a' to be in ReadonlyArray, should succeed`)
+  private aToBeInReadonlySuccess() {
+    const readonlyArray: ReaonlyArray<string> = ['a', 'b', 'c'];
+    expect.toBeIn('a', readonlyArray);
+  }  
 
   @Test(`'a' to be in, should fail`)
   private aToBeInFail() {