fix(NODE-3640): Fix Int32 constructor to coerce its argument to int32 (#466)

Author: gjchong25

src/int_32.ts

@@ -25,7 +25,7 @@ export class Int32 {
       value = value.valueOf();
     }
 
-    this.value = +value;
+    this.value = +value | 0;
   }
 
   /**

test/node/int_32_tests.js

@@ -9,32 +9,56 @@ describe('Int32', function () {
     const hexValue = 0x2a;
     const octalValue = 0o52;
     const value = 42;
+    const upperBoundValue = 0x7fffffff;
+    const lowerBoundValue = -0x80000000;
+    const outOfUpperBoundValue = 0x80000000;
+    const outOfLowerBoundValue = -0x80000001;
 
-    it('Primitive number', function (done) {
+    it('should accept primitive numbers', function (done) {
       expect(new Int32(value).valueOf()).to.equal(value);
       done();
     });
 
-    it('Number object', function (done) {
+    it('should accept number objects', function (done) {
       expect(new Int32(new Number(value)).valueOf()).to.equal(value);
       done();
     });
 
-    it('String Hex', function (done) {
+    it('should accept string Hex', function (done) {
       expect(new Int32(strHexValue).valueOf()).to.equal(value);
       done();
     });
 
-    it('Hex', function (done) {
+    it('should accept hex', function (done) {
       expect(new Int32(hexValue).valueOf()).to.equal(value);
       done();
     });
 
-    it('Octal', function (done) {
+    it('should accept octal', function (done) {
       expect(new Int32(octalValue).valueOf()).to.equal(value);
       done();
     });
 
+    it('should accept int32 minimum input of -0x80000000', function (done) {
+      expect(new Int32(lowerBoundValue).valueOf()).to.equal(lowerBoundValue);
+      done();
+    });
+
+    it('should accept int32 maximum input of 0x7fffffff', function (done) {
+      expect(new Int32(upperBoundValue).valueOf()).to.equal(upperBoundValue);
+      done();
+    });
+
+    it('should truncate the input bits to int32 for inputs smaller than -0x80000000', function (done) {
+      expect(new Int32(outOfLowerBoundValue).valueOf()).to.equal(0x7fffffff);
+      done();
+    });
+
+    it('should truncate the input bits to int32 for inputs larger than 0x7fffffff', function (done) {
+      expect(new Int32(outOfUpperBoundValue).valueOf()).to.equal(-0x80000000);
+      done();
+    });
+
     it('should equal zero', function () {
       const prop = 'key';
       const zero = BSON.serialize({ [prop]: new Int32(0) }).toString();
@@ -45,7 +69,7 @@ describe('Int32', function () {
       });
     });
 
-    it('should equal fortyTwo', function () {
+    it('should have serialization consistency across different representations of 42', function () {
       const prop = 'key';
       const fortyTwo = BSON.serialize({ [prop]: new Int32(value) }).toString();
       // should equal fortyTwo
@@ -58,7 +82,7 @@ describe('Int32', function () {
 
   describe('toString', () => {
     it('should serialize to a string', () => {
-      const testNumber = Math.floor(Math.random() * 0xffffffff);
+      const testNumber = 0x7fffffff;
       const int32 = new Int32(testNumber);
       expect(int32.toString()).to.equal(testNumber.toString());
     });
@@ -67,7 +91,7 @@ describe('Int32', function () {
 
     for (const radix of testRadices) {
       it(`should support radix argument: ${radix}`, () => {
-        const testNumber = Math.floor(Math.random() * 0xffffffff);
+        const testNumber = 0x7fffffff;
         const int32 = new Int32(testNumber);
         expect(int32.toString(radix)).to.equal(testNumber.toString(radix));
       });