Added control digit validation.

src/ValidationErrorCode.ts

@@ -1,5 +1,6 @@
 export enum ValidationErrorCode {
     InvalidBirthDate,           // Birth date is not a valid date.
     InvalidIndividualDigits,    // Birth date does not match individual digits.
-    InvalidSsnFormat            // Provided SSN does not conform to the expected format.
+    InvalidSsnFormat,           // Provided SSN does not conform to the expected format.
+    InvalidControlDigits        // Control digits do not match birth date and individual digits.
 }

src/getDateOfBirthFromSsn.ts

@@ -5,4 +5,6 @@ export const getDateOfBirthFromSsn = (value: string): Date => {
     yearOfBirth += yearOfBirth > 50 ? 1900 : 2000
 
     return new Date(`${yearOfBirth}-${monthOfBirth}-${dayOfBirth}T00:00:00.000Z`)
-}
+}
+
+export const validateDateOfBirth = (dateOfBirth: Date): boolean => dateOfBirth instanceof Date && !isNaN(dateOfBirth.getTime())

src/validateControlDigits.ts

@@ -0,0 +1,33 @@
+const getFirstControlDigit = (d1: number, d2: number, m1: number, m2: number, y1: number, y2: number, i1: number, i2: number, i3: number): number => {
+    const firstControlDigit = 11 - ((3 * d1 + 7 * d2 + 6 * m1 + 1 * m2 + 8 * y1 + 9 * y2 + 4 * i1 + 5 * i2 + 2 * i3) % 11)
+    return firstControlDigit === 11 ? 0 : firstControlDigit
+}
+
+const getSecondControlDigit = (d1: number, d2: number, m1: number, m2: number, y1: number, y2: number, i1: number, i2: number, i3: number, c1: number): number => {
+    const secondControlDigit = 11 - ((5 * d1 + 4 * d2 + 3 * m1 + 2 * m2 + 7 * y1 + 6 * y2 + 5 * i1 + 4 * i2 + 3 * i3 + 2 * c1) % 11)
+    return secondControlDigit === 11 ? 0 : secondControlDigit
+}
+
+const getControlDigitsFromSsn = (ssn: string): Array<number> => {
+    const d1 = Number(ssn.slice(0, 1))
+    const d2 = Number(ssn.slice(1, 2))
+    const m1 = Number(ssn.slice(2, 3))
+    const m2 = Number(ssn.slice(3, 4))
+    const y1 = Number(ssn.slice(4, 5))
+    const y2 = Number(ssn.slice(5, 6))
+    const i1 = Number(ssn.slice(6, 7))
+    const i2 = Number(ssn.slice(7, 8))
+    const i3 = Number(ssn.slice(8, 9))
+    const c1 = getFirstControlDigit(d1, d2, m1, m2, y1, y2, i1, i2, i3)
+    const c2 = getSecondControlDigit(d1, d2, m1, m2, y1, y2, i1, i2, i3, c1)
+
+    return [c1, c2]
+}
+
+export const validateControlDigits = (ssn: string): boolean => {
+    const firstControlDigit = Number(ssn.slice(9, 10))
+    const secondControlDigit = Number(ssn.slice(10, 11))
+    const actualControlDigits = getControlDigitsFromSsn(ssn)
+
+    return firstControlDigit === actualControlDigits[0] && secondControlDigit === actualControlDigits[1]
+}

src/validateSsn.ts

@@ -1,4 +1,5 @@
-import { getDateOfBirthFromSsn } from './getDateOfBirthFromSsn'
+import { getDateOfBirthFromSsn, validateDateOfBirth } from './getDateOfBirthFromSsn'
+import { validateControlDigits } from './validateControlDigits'
 import { validateIndividualDigits } from './validateIndividualDigits'
 import { ValidationErrorCode } from './ValidationErrorCode'
 import { ValidationResult } from './ValidationResult'
@@ -7,11 +8,11 @@ export const validateSsn = (value: string): ValidationResult => {
     if(!/\d{11}/.test(value)) return new ValidationResult(ValidationErrorCode.InvalidSsnFormat)
 
     const dateOfBirth = getDateOfBirthFromSsn(value)
-    if(!(dateOfBirth instanceof Date) || isNaN(dateOfBirth.getTime())) return new ValidationResult(ValidationErrorCode.InvalidBirthDate)
-
     const individualDigits = Number(value.slice(6, 9))
-    if(!validateIndividualDigits(individualDigits, dateOfBirth)) return new ValidationResult(ValidationErrorCode.InvalidIndividualDigits)
 
+    if(!validateDateOfBirth(dateOfBirth)) return new ValidationResult(ValidationErrorCode.InvalidBirthDate)
+    if(!validateIndividualDigits(individualDigits, dateOfBirth)) return new ValidationResult(ValidationErrorCode.InvalidIndividualDigits)
+    if(!validateControlDigits(value)) return new ValidationResult(ValidationErrorCode.InvalidControlDigits)
 
     return new ValidationResult()
 }

tests/getDateOfBirthFromSsn.spec.ts

@@ -1,6 +1,6 @@
 import { getDateOfBirthFromSsn } from '../src/getDateOfBirthFromSsn'
 
-describe('it should suceed', () => {
+describe('it should succeed', () => {
     test('when the date of birth is valid', () => {
         // arrange
         const ssn = '01015111111'

tests/toBeExpectedBoolean.ts → tests/toBeWithErrorMessage.ts

@@ -3,16 +3,16 @@ export {}
 declare global {
     namespace jest {
         interface Matchers<R> {
-            toBeExpectedBoolean(expected: boolean, context: string): CustomMatcherResult
+            toBeWithErrorMessage(expected: boolean, errorMessage: string): CustomMatcherResult
         }
     }
 }
 
 expect.extend({
-    toBeExpectedBoolean(received: boolean, expected: boolean, context: string) {
+    toBeWithErrorMessage(received: boolean, expected: boolean, errorMessage: string) {
         return {
             pass: received === expected,
-            message: () => `Expected values to be equal, but they weren't. Received: ${received}. Context: ${context}`
+            message: () => `Expected values to be equal, but they weren't. Received: ${received}. Error message: ${errorMessage}`
         }
     }
 })

tests/validateControlDigits.ts

@@ -0,0 +1,27 @@
+import { validateControlDigits } from '../src/getControlDigitsFromSsn'
+
+describe('it should succeed', () => {
+    test('when the control digits are valid', () => {
+        // arrange
+        const ssn = '01015111190'
+
+        // act
+        const result = validateControlDigits(ssn)
+
+        // assert
+        expect(result).toBe(true)
+    })
+})
+
+describe('it should fail', () => {
+    test('when the control digits are invalid', () => {
+        // arrange
+        const ssn = '01015111111'
+
+        // act
+        const result = validateControlDigits(ssn)
+
+        // assert
+        expect(result).toBe(false)
+    })
+})

tests/validateIndividualDigits.spec.ts

@@ -1,5 +1,5 @@
 import { validateIndividualDigits } from '../src/validateIndividualDigits'
-import './toBeExpectedBoolean'
+import './toBeWithErrorMessage'
 
 const IS_VERBOSE = Boolean(process.env.TEST_VALIDATE_INDIVIDUAL_DIGITS_VERBOSE || false)
 const ITERATIONS = Number(process.env.TEST_VALIDATE_INDIVIDUAL_DIGITS_ITERATIONS || 1000)
@@ -29,7 +29,7 @@ const ITERATIONS = Number(process.env.TEST_VALIDATE_INDIVIDUAL_DIGITS_ITERATIONS
         const result = validateIndividualDigits(individualDigits, dateofBirth)
 
         // assert
-        expect(result).toBeExpectedBoolean(shouldSucceed, `[individualDigits:${individualDigits}, dateOfBirth:${dateofBirth.toISOString()}, expected:${shouldSucceed}]`)
+        expect(result).toBeWithErrorMessage(shouldSucceed, `[individualDigits:${individualDigits}, dateOfBirth:${dateofBirth.toISOString()}, expected:${shouldSucceed}]`)
      }
  }
 

tests/validateSsn.spec.ts

@@ -1,11 +1,11 @@
 import { validateSsn } from '../src/validateSsn'
 import { ValidationErrorCode } from '../src/ValidationErrorCode'
-import './toBeExpectedBoolean'
+import './toBeWithErrorMessage'
 
 describe('it should succeed', () => {
     test('when the ssn is valid', () => {
         // arrange
-        const ssn = '01015111111'
+        const ssn = '01015111190'
 
         // act
         const result = validateSsn(ssn)