diff --git a/test/average.test.js b/test/average.test.js
index 47efaa0d8..5cc7d99a6 100644
--- a/test/average.test.js
+++ b/test/average.test.js
@@ -4,10 +4,10 @@ const {average} = require('./_30s.js');
 test('average is a Function', () => {
   expect(average).toBeInstanceOf(Function);
 });
-test('average(true) returns 0', () => {
+test('average(true) returns 1', () => {
   expect(average(true) === 1).toBeTruthy();
 });
-test('average(false) returns 1', () => {
+test('average(false) returns 0', () => {
   expect(average(false) === 0).toBeTruthy();
 });
 test('average(9, 1) returns 5', () => {
@@ -25,10 +25,10 @@ test('average(1, 2, 3) returns 2', () => {
 test('average(null) returns 0', () => {
   expect(average(null)).toBe(0);
 });
-test('average(1, 2, 3) returns NaN', () => {
+test('average(undefined) returns NaN', () => {
   expect(isNaN(average(undefined))).toBeTruthy();
 });
-test('average(String) returns NaN', () => {
+test('average("String") returns NaN', () => {
   expect(isNaN(average('String'))).toBeTruthy();
 });
 test('average({ a: 123}) returns NaN', () => {
diff --git a/test/compact.test.js b/test/compact.test.js
index e63c47b8e..5469b1ccf 100644
--- a/test/compact.test.js
+++ b/test/compact.test.js
@@ -5,7 +5,7 @@ test('compact is a Function', () => {
   expect(compact).toBeInstanceOf(Function);
 });
 test('Removes falsey values from an array', () => {
-  expect(compact([0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34])).toEqual([
+  expect(compact([0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34, null, undefined])).toEqual([
     1,
     2,
     3,
diff --git a/test/countOccurrences.test.js b/test/countOccurrences.test.js
index 5ac6c1e1d..2213fd39e 100644
--- a/test/countOccurrences.test.js
+++ b/test/countOccurrences.test.js
@@ -7,3 +7,6 @@ test('countOccurrences is a Function', () => {
 test('Counts the occurrences of a value in an array', () => {
   expect(countOccurrences([1, 1, 2, 1, 2, 3], 1)).toEqual(3);
 });
+test('Works with different types in the same array', () => {
+  expect(countOccurrences([1, 1, 2, 1, 2, 3, '1', true], 1)).toEqual(3);
+});
diff --git a/test/filterNonUnique.test.js b/test/filterNonUnique.test.js
index 459c67282..2d94bb77f 100644
--- a/test/filterNonUnique.test.js
+++ b/test/filterNonUnique.test.js
@@ -7,3 +7,10 @@ test('filterNonUnique is a Function', () => {
 test('Filters out the non-unique values in an array', () => {
   expect(filterNonUnique([1, 2, 2, 3, 4, 4, 5])).toEqual([1, 3, 5]);
 });
+test('Works with multiple types of values in the same array', () => {
+  expect(filterNonUnique([1, 2, 2, 3, 4, 4, 5, true, 'repeated text', 'repeated text', 'unique text'])).toEqual([1, 3, 5, true, 'unique text']);
+});
+test('No error on empty array', () => {
+  expect(filterNonUnique([])).toEqual([]);
+});
+
diff --git a/test/findLastKey.test.js b/test/findLastKey.test.js
index 405f17496..5ce260b8a 100644
--- a/test/findLastKey.test.js
+++ b/test/findLastKey.test.js
@@ -4,7 +4,7 @@ const {findLastKey} = require('./_30s.js');
 test('findLastKey is a Function', () => {
   expect(findLastKey).toBeInstanceOf(Function);
 });
-test('eturns the appropriate key', () => {
+test('returns the appropriate key', () => {
   expect(
     findLastKey(
       {
diff --git a/test/squareSum.test.js b/test/squareSum.test.js
index 13b31a2af..69b6b8962 100644
--- a/test/squareSum.test.js
+++ b/test/squareSum.test.js
@@ -7,3 +7,11 @@ test('squareSum is a Function', () => {
 test('squareSum returns the proper result', () => {
   expect(squareSum(2, 3, 4)).toBe(29);
 });
+
+test('works with negative numbers', () => {
+  expect(squareSum(-2, 3, -4)).toBe(29);
+});
+
+test('NaN when parameters have text', () => {
+  expect(squareSum(-2, 3, -4, 'text')).toBe(NaN);
+});
diff --git a/test/uniqueSymmetricDifference.test.js b/test/uniqueSymmetricDifference.test.js
index d9fa598b6..eaf97a6a1 100644
--- a/test/uniqueSymmetricDifference.test.js
+++ b/test/uniqueSymmetricDifference.test.js
@@ -10,3 +10,13 @@ test('Returns the symmetric difference between two arrays.', () => {
 test('Does not return duplicates from one array', () => {
   expect(uniqueSymmetricDifference([1, 2, 2], [1, 3, 1])).toEqual([2, 3]);
 });
+test('Works with different size arrays', () => {
+  expect(uniqueSymmetricDifference([1, 2, 2, 4], [1, 3, 1, 4, 5, 6])).toEqual([2, 3, 5, 6]);
+});
+test('Works with different types in the same array', () => {
+  expect(uniqueSymmetricDifference([1, 2, 'duplicate text', 'unique text'], [1, 3, 'duplicate text'])).toEqual([2, 'unique text', 3]);
+});
+test('Works when one array is empty', () => {
+  expect(uniqueSymmetricDifference([1, 2, 2, 3], [])).toEqual([1, 2, 3]);
+});
+