From 07a58f56ea0eccfd236bd49326a4d3dfeb6a9ad4 Mon Sep 17 00:00:00 2001
From: Nicolas DUBIEN <github@dubien.org>
Date: Thu, 23 May 2024 18:29:48 +0000
Subject: [PATCH] test: Add property-based tests

Following the discussion started on https://github.com/chaijs/loupe/pull/79. I'm opening this PR as an opened question and suggestion to better cover the library and its edge-cases.

First, what is property-based testing?

It's a technic coming from functional world and aiming to help devs into detecting edge cases without having them to think of them too much.

Why, property-based testing?

Well, in order to reduce the risks of bugs and potentially regressions on key libraries.

Could it found problems?

Well, probably. I tried another property but I'm not sure whether or not the failure is considered as ok or not. As such I'm not sure of what to expect from truncate so I was not able to make a decision.

```js
it('produces strings with at most <truncate> characters', () => {
  fc.assert(
    fc.property(
      fc.anything({
        withBigInt: true,
        withBoxedValues: true,
        withDate: true,
        withMap: true,
        withNullPrototype: true,
        withObjectString: true,
        withSet: true,
        withSparseArray: true,
        withTypedArray: true,
        withUnicodeString: true,
      }),
      fc.nat(),
      (source, truncate) => {
        const output = inspect(source, { truncate })
        expect(output).to.have.lengthOf.at.most(truncate)
      }
    )
  )
})
```

Who am I?

I'm the author of fast-check, the library added by this PR. It's the leading property-based testing library today.
---
 package-lock.json | 39 +++++++++++++++++++++++++++++++++++++++
 package.json      |  1 +
 test/property.js  | 28 ++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+)
 create mode 100644 test/property.js

diff --git a/package-lock.json b/package-lock.json
index 529de81..61dc299 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -25,6 +25,7 @@
         "eslint-config-strict": "^14.0.1",
         "eslint-plugin-filenames": "^1.3.2",
         "eslint-plugin-prettier": "^3.3.1",
+        "fast-check": "^3.19.0",
         "husky": "^4.3.8",
         "mocha": "^10.2.0",
         "nyc": "^15.1.0",
@@ -5235,6 +5236,28 @@
         "@types/yauzl": "^2.9.1"
       }
     },
+    "node_modules/fast-check": {
+      "version": "3.19.0",
+      "resolved": "https://registry.npmjs.org/fast-check/-/fast-check-3.19.0.tgz",
+      "integrity": "sha512-CO2JX/8/PT9bDGO1iXa5h5ey1skaKI1dvecERyhH4pp3PGjwd3KIjMAXEg79Ps9nclsdt4oPbfqiAnLU0EwrAQ==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://github.com/sponsors/dubzzz"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/fast-check"
+        }
+      ],
+      "dependencies": {
+        "pure-rand": "^6.1.0"
+      },
+      "engines": {
+        "node": ">=8.0.0"
+      }
+    },
     "node_modules/fast-deep-equal": {
       "version": "3.1.3",
       "resolved": "https://registry.npmjs.org/fast-deep-equal/-/fast-deep-equal-3.1.3.tgz",
@@ -13658,6 +13681,22 @@
         }
       }
     },
+    "node_modules/pure-rand": {
+      "version": "6.1.0",
+      "resolved": "https://registry.npmjs.org/pure-rand/-/pure-rand-6.1.0.tgz",
+      "integrity": "sha512-bVWawvoZoBYpp6yIoQtQXHZjmz35RSVHnUOTefl8Vcjr8snTPY1wnpSPMWekcFwbxI6gtmT7rSYPFvz71ldiOA==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "individual",
+          "url": "https://github.com/sponsors/dubzzz"
+        },
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/fast-check"
+        }
+      ]
+    },
     "node_modules/q": {
       "version": "1.5.1",
       "resolved": "https://registry.npmjs.org/q/-/q-1.5.1.tgz",
diff --git a/package.json b/package.json
index 83a9e6f..ef8ea38 100644
--- a/package.json
+++ b/package.json
@@ -115,6 +115,7 @@
     "eslint-config-strict": "^14.0.1",
     "eslint-plugin-filenames": "^1.3.2",
     "eslint-plugin-prettier": "^3.3.1",
+    "fast-check": "^3.19.0",
     "husky": "^4.3.8",
     "mocha": "^10.2.0",
     "nyc": "^15.1.0",
diff --git a/test/property.js b/test/property.js
new file mode 100644
index 0000000..4e9e2a2
--- /dev/null
+++ b/test/property.js
@@ -0,0 +1,28 @@
+import inspect from '../lib/index.js'
+import { expect } from 'chai'
+import fc from 'fast-check'
+
+describe('property', () => {
+  it('produces valid UTF-16 strings whatever the source', () => {
+    fc.assert(
+      fc.property(
+        fc.anything({
+          withBigInt: true,
+          withBoxedValues: true,
+          withDate: true,
+          withMap: true,
+          withNullPrototype: true,
+          withObjectString: true,
+          withSet: true,
+          withSparseArray: true,
+          withTypedArray: true,
+          withUnicodeString: true,
+        }),
+        fc.option(fc.nat(), { nil: undefined }),
+        (source, truncate) => {
+          expect(() => encodeURI(inspect(source, { truncate }))).not.to.throw()
+        }
+      )
+    )
+  })
+})