test: Improved tests

* Added additional tests for input validation handling and data structure constraints
* Removed test related to string matching

src/index.test.js

@@ -4,6 +4,42 @@ import { dirname } from 'node:path'
 import { fileURLToPath } from 'node:url'
 import isApng from '../dist/index.mjs'
 
+/** Input validation tests */
+
+test('returns false on number 0 input', (t) => {
+  t.false(isApng(0))
+})
+
+test('returns false on number 1 input', (t) => {
+  t.false(isApng(1))
+})
+
+test('returns false on empty string input', (t) => {
+  t.false(isApng(''))
+})
+
+test('returns false on non-empty string input', (t) => {
+  t.false(isApng('string'))
+})
+
+test('returns false on boolean true input', (t) => {
+  t.false(isApng(true))
+})
+
+test('returns false on boolean false input', (t) => {
+  t.false(isApng(false))
+})
+
+test('returns false on object input', (t) => {
+  t.false(isApng({}))
+})
+
+test('returns false on array input', (t) => {
+  t.false(isApng([]))
+})
+
+/** Real image tests */
+
 const dir =
   typeof __dirname !== 'undefined'
     ? __dirname
@@ -19,15 +55,17 @@ test('returns false on static PNG', (t) => {
   t.false(check(dir + '/images/static.png'))
 })
 
+test('returns false on static PNG with `acTL` text in metadata', (t) => {
+  t.false(check(dir + '/images/staticWithMetadata.png'))
+})
+
 test('returns false on JPG', (t) => {
   t.false(check(dir + '/images/static.jpg'))
 })
 
-test('returns false on static PNG with `acTL` text in metadata', (t) => {
-  t.false(check(dir + '/images/staticWithMetadata.png'))
-})
+/** Mock data tests */
 
-test('returns true when IDAT follows acTL', (t) => {
+test('returns true when acTL precedes any IDAT', (t) => {
   t.true(
     isApng(
       new Uint8Array([
@@ -43,6 +81,31 @@ test('returns true when IDAT follows acTL', (t) => {
         0x00, 0x00, 0x00, 0x00,
         // Chunk type: IDAT
         0x49, 0x44, 0x41, 0x54,
+        // Chunk CRC
+        0x00, 0x00, 0x00, 0x00,
+      ]),
+    ),
+  )
+})
+
+test('returns false when any IDAT precedes acTL', (t) => {
+  t.false(
+    isApng(
+      new Uint8Array([
+        // PNG header
+        0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
+        // Chunk length: 0
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk type: IDAT
+        0x49, 0x44, 0x41, 0x54,
+        // Chunk CRC
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk length: 0
+        0x00, 0x00, 0x00, 0x00,
+        // Chunk type: acTL
+        0x61, 0x63, 0x54, 0x4c,
+        // Chunk CRC
+        0x00, 0x00, 0x00, 0x00,
       ]),
     ),
   )
@@ -60,42 +123,36 @@ test('returns false when acTL is not a chunk type', (t) => {
         0x00, 0x00, 0x00, 0x01,
         // Chunk data: acTL
         0x61, 0x63, 0x54, 0x4c,
+        // Chunk CRC
+        0x00, 0x00, 0x00, 0x00,
       ]),
     ),
   )
 })
 
-test('returns false when IDAT precedes acTL', (t) => {
+test('returns false on too small PNG', (t) => {
   t.false(
     isApng(
       new Uint8Array([
         // PNG header
         0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
-        // Chunk length: 0
-        0x00, 0x00, 0x00, 0x00,
-        // Chunk type: IDAT
-        0x49, 0x44, 0x41, 0x54,
-        // Chunk CRC
-        0x00, 0x00, 0x00, 0x00,
-        // Chunk length: 0
-        0x00, 0x00, 0x00, 0x00,
-        // Chunk type: acTL
-        0x61, 0x63, 0x54, 0x4c,
+        // Content omitted
       ]),
     ),
   )
 })
 
-test('chunks should be found when preceded by a partial of themselves', (t) => {
-  t.true(
+test('returns false on invalid chunk', (t) => {
+  t.false(
     isApng(
       new Uint8Array([
         // PNG header
         0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
-        // Chunk length: a
-        0x00, 0x00, 0x00, 0x61,
-        // Chunk type: acTL
-        0x61, 0x63, 0x54, 0x4c,
+        // Chunk length: 4
+        0x00, 0x00, 0x00, 0x04,
+        // Chunk type: any
+        0x00, 0x00, 0x00, 0x01,
+        // Chunk CRC omitted
       ]),
     ),
   )