diff --git a/src/common/protojs.test.mjs b/src/common/protojs.test.mjs
new file mode 100644
index 0000000..b5ee44c
--- /dev/null
+++ b/src/common/protojs.test.mjs
@@ -0,0 +1,148 @@
+/* eslint-disable no-sparse-arrays */
+import * as protojs from './protojs.js';
+
+const objectLike1 = {
+  '2': [1, 2, 3],
+};
+
+const arrayLike1 = [
+  undefined,
+  [1, 2, 3],
+];
+
+const rObjectLike1 = [
+  ,
+  undefined,
+  [, 1, 2, 3],
+];
+
+const objectLike2 = {
+  '1': {
+    '1': 12,
+    '2': [
+      {
+        '6': [false, false, false],
+        '7': {
+          '1': false,
+          '2': 'Hola',
+        },
+      },
+      {
+        '6': [true, true, false],
+        '7': {
+          '1': false,
+          '2': 'Test',
+        },
+      },
+      {
+        '6': [],
+        '7': {
+          '1': true,
+          '2': 'Bye',
+        },
+      },
+    ],
+    '3': 1663,
+  },
+};
+
+const arrayLike2 = [[
+  12,
+  [
+    [
+      undefined, undefined, undefined, undefined, undefined,
+      [false, false, false],
+      [
+        false,
+        'Hola',
+      ]
+    ],
+    [
+      undefined, undefined, undefined, undefined, undefined,
+      [true, true, false],
+      [
+        false,
+        'Test',
+      ]
+    ],
+    [
+      undefined, undefined, undefined, undefined, undefined, [],
+      [
+        true,
+        'Bye',
+      ]
+    ],
+  ],
+  1663,
+]];
+
+const rObjectLike2 = [, [
+  ,
+  12,
+  [
+    ,
+    [
+      , undefined, undefined, undefined, undefined, undefined,
+      [, false, false, false],
+      [
+        ,
+        false,
+        'Hola',
+      ]
+    ],
+    [
+      , undefined, undefined, undefined, undefined, undefined,
+      [, true, true, false],
+      [
+        ,
+        false,
+        'Test',
+      ]
+    ],
+    [
+      , undefined, undefined, undefined, undefined, undefined, [],
+      [
+        ,
+        true,
+        'Bye',
+      ]
+    ],
+  ],
+  1663,
+]];
+
+test('can convert object-like to array-like', () => {
+  // [ object-like input, array-like verified output ]
+  const entries = [
+    [objectLike1, arrayLike1],
+    [rObjectLike1, arrayLike1],
+    [objectLike2, arrayLike2],
+    [rObjectLike2, arrayLike2],
+  ];
+
+  entries.forEach(([input, verifiedOutput]) => {
+    const converted = protojs.inverseCorrectArrayKeys(input);
+    expect(converted).toStrictEqual(verifiedOutput);
+  });
+});
+
+test('can convert array-like to object-like', () => {
+  // [ array-like input, object-like verified output ]
+  const entries = [
+    [arrayLike1, rObjectLike1],
+    [arrayLike2, rObjectLike2],
+  ];
+
+  entries.forEach(([input, verifiedOutput]) => {
+    const converted = protojs.correctArrayKeys(input);
+    expect(converted).toStrictEqual(verifiedOutput);
+  });
+});
+
+test('empty object can be converted to array-like form', () => {
+  const object = {
+    1: {},
+  };
+  const converted = protojs.inverseCorrectArrayKeys(object);
+  expect(converted).toStrictEqual([[]]);
+});