Within and closeTo matchers for BigNumber (TrueFiEng#416)

* Within and closeTo matchers for BigNumber * Add missing failing test cases * Add examples of new matchers to documentation Co-authored-by: Tetiana Platonova <[email protected]>
bnymnDev · Feb 26, 2021 · 9fd9661 · 9fd9661
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diff --git a/docs/source/matchers.rst b/docs/source/matchers.rst
@@ -20,7 +20,12 @@ Testing equality of big numbers:
 
   expect(await token.balanceOf(wallet.address)).to.equal(993);
 
-Available matchers for BigNumbers are: `equal`, `eq`, `above`, `gt`, `gte`, `below`, `lt`, `lte`, `least`, `most`.
+Available matchers for BigNumbers are: `equal`, `eq`, `above`, `gt`, `gte`, `below`, `lt`, `lte`, `least`, `most`, `within`, `closeTo`.
+
+.. code-block:: ts
+
+  expect(BigNumber.from(100)).to.be.within(BigNumber.from(99), BigNumber.from(101));
+  expect(BigNumber.from(100)).to.be.closeTo(BigNumber.from(101), 10);
 
 Emitting events
 ---------------

diff --git a/waffle-chai/src/matchers/bigNumber.ts b/waffle-chai/src/matchers/bigNumber.ts
@@ -24,6 +24,10 @@ export function supportBigNumber(
     'lte',
     override('lte', 'less than or equal', utils)
   );
+
+  Assertion.overwriteMethod('within', overrideWithin(utils));
+
+  Assertion.overwriteMethod('closeTo', overrideCloseTo(utils));
 }
 
 type Methods = 'eq' | 'gt' | 'lt' | 'gte' | 'lte';
@@ -59,3 +63,48 @@ function overwriteBigNumberFunction(
     }
   };
 }
+
+function overrideWithin(utils: Chai.ChaiUtils) {
+  return (_super: (...args: any[]) => any) => overwriteBigNumberWithin(_super, utils);
+}
+
+function overwriteBigNumberWithin(_super: (...args: any[]) => any, chaiUtils: Chai.ChaiUtils) {
+  return function (this: Chai.AssertionStatic, ...args: any[]) {
+    const [start, finish] = args;
+    const expected = chaiUtils.flag(this, 'object');
+    if (BigNumber.isBigNumber(expected) || BigNumber.isBigNumber(start) || BigNumber.isBigNumber(finish)) {
+      this.assert(
+        BigNumber.from(start).lte(expected) && BigNumber.from(finish).gte(expected),
+        `Expected "${expected}" to be within [${[start, finish]}]`,
+        `Expected "${expected}" NOT to be within [${[start, finish]}]`,
+        [start, finish],
+        expected
+      );
+    } else {
+      _super.apply(this, args);
+    }
+  };
+}
+
+function overrideCloseTo(utils: Chai.ChaiUtils) {
+  return (_super: (...args: any[]) => any) =>
+    overwriteBigNumberCloseTo(_super, utils);
+}
+
+function overwriteBigNumberCloseTo(_super: (...args: any[]) => any, chaiUtils: Chai.ChaiUtils) {
+  return function (this: Chai.AssertionStatic, ...args: any[]) {
+    const [actual, delta] = args;
+    const expected = chaiUtils.flag(this, 'object');
+    if (BigNumber.isBigNumber(expected) || BigNumber.isBigNumber(actual) || BigNumber.isBigNumber(delta)) {
+      this.assert(
+        BigNumber.from(expected).sub(actual).abs().lte(delta),
+        `Expected "${expected}" to be within ${delta} of ${actual}`,
+        `Expected "${expected}" NOT to be within ${delta} of ${actual}`,
+        `A number between ${actual.sub(delta)} and ${actual.sub(delta)}`,
+        expected
+      );
+    } else {
+      _super.apply(this, args);
+    }
+  };
+}
diff --git a/waffle-chai/test/matchers/bigNumber.test.ts b/waffle-chai/test/matchers/bigNumber.test.ts
@@ -122,4 +122,43 @@ describe('UNIT: BigNumber matchers', () => {
       checkAll(10, 9, (a, b) => expect(a).not.to.be.lte(b));
     });
   });
+
+  describe('within', () => {
+    it('.to.be.within', () => {
+      expect(BigNumber.from(100)).to.be.within(BigNumber.from(99), BigNumber.from(101));
+    });
+
+    it('.not.to.be.within', () => {
+      expect(BigNumber.from(100)).not.to.be.within(BigNumber.from(101), BigNumber.from(102));
+      expect(BigNumber.from(100)).not.to.be.within(BigNumber.from(98), BigNumber.from(99));
+    });
+
+    it('expect to throw on error', () => {
+      expect(
+        () => expect(BigNumber.from(100)).to.be.within(BigNumber.from(80), BigNumber.from(90))
+      ).to.throw(AssertionError, 'Expected "100" to be within [80,90]');
+      expect(
+        () => expect(BigNumber.from(100)).not.to.be.within(BigNumber.from(99), BigNumber.from(101))
+      ).to.throw(AssertionError, 'Expected "100" NOT to be within [99,101]');
+    });
+  });
+
+  describe('closeTo', () => {
+    it('.to.be.closeTo', () => {
+      expect(BigNumber.from(100)).to.be.closeTo(BigNumber.from(101), 10);
+    });
+
+    it('.not.to.be.closeTo', () => {
+      expect(BigNumber.from(100)).not.to.be.closeTo(BigNumber.from(111), 10);
+    });
+
+    it('expect to throw on error', () => {
+      expect(
+        () => expect(BigNumber.from(100)).to.be.closeTo(BigNumber.from(111), 10)
+      ).to.throw(AssertionError, 'Expected "100" to be within 10 of 111');
+      expect(
+        () => expect(BigNumber.from(100)).not.to.be.closeTo(BigNumber.from(101), 10)
+      ).to.throw(AssertionError, 'Expected "100" NOT to be within 10 of 101');
+    });
+  });
 });