Throw error when array does not have the same size (#47)

assert/src/index.ts

@@ -10,6 +10,11 @@ interface ExtraAssertions {
   ): asserts actual is Partial<T>
 }
 
+const formatValues = <A, E>(actual: A, expected: E) => `\n\nActual:
+${JSON.stringify(actual, undefined, 2)}\n
+Expected:
+${JSON.stringify(expected, undefined, 2)}\n`
+
 const assertions: ExtraAssertions = {
   objectContains<T extends Record<string, any>>(
     actual: Record<string, any>,
@@ -19,7 +24,11 @@ const assertions: ExtraAssertions = {
     debug('[ASSERT] objectContains', actual, expected)
 
     if (typeof actual !== 'object' || typeof expected !== 'object') {
-      throw new Error('Both actual and expected values must be objects');
+      throw new Error(`Both actual and expected values must be objects. ${formatValues(actual, expected)}`);
+    }
+
+    if (Array.isArray(actual) && Array.isArray(expected) && actual.length !== expected.length) {
+      throw new Error(`Both actual and expected should have the same number of elements. ${formatValues(actual, expected)}`);
     }
 
     const expectedKeys = Object.keys(expected);

assert/test/index.test.ts

@@ -12,10 +12,29 @@ test('It partially check object properties', () => {
 test('It fails when object properties does not match', () => {
   const actual = {a: 'b', c: 'd'}
   const expected = {c: 'e'}
+  let asserted  = 0
 
   try {
     extraAssert.objectContains(actual, expected)
   } catch (error) {
     nodeAssert.equal(error.code, 'ERR_ASSERTION')
+    asserted = 1
   }
+
+  nodeAssert.ok(asserted)
+})
+
+test('It fails when array does not have the same size', () => {
+  const actual = [{a: 'b'}, {c: 'd'}]
+  const expected = [{c: 'e'}]
+  let asserted  = 0
+
+  try {
+    extraAssert.objectContains(actual, expected)
+  } catch (error) {
+    nodeAssert.ok(error.message.indexOf('Both actual and expected should have the same number of elements') !== -1)
+    asserted = 1
+  }
+
+  nodeAssert.ok(asserted)
 })