test: rewrite mersenne tests

src/mersenne.ts

@@ -19,7 +19,7 @@ export class Mersenne {
   }
 
   /**
-   * Generates a random number between min and max (inclusive).
+   * Generates a random number between [min, max)'.
    *
    * @param max The maximum number. Defaults to `0`.
    * @param min The minimum number. Defaults to `32768`. Required if `max` is set.

test/mersenne.spec.ts

@@ -0,0 +1,211 @@
+import { beforeAll, beforeEach, describe, expect, it } from 'vitest';
+import { Mersenne } from '../src/mersenne';
+
+type SeededRun = {
+  seed: number | number[];
+  expectations: SeededRunExpectations;
+};
+type SeededRunExpectations = {
+  rand: {
+    noArgs: number;
+    minMax: { max?: number; min?: number; expected?: number; skip?: boolean }[];
+  };
+};
+
+const seededRuns: SeededRun[] = [
+  {
+    seed: 42,
+    expectations: {
+      rand: {
+        noArgs: 12272,
+        minMax: [
+          { max: 100, min: 0, expected: 37 },
+          { max: undefined, min: 0, expected: 12272 },
+          { max: 100, min: undefined, expected: 37, skip: true },
+        ],
+      },
+    },
+  },
+  {
+    seed: 1337,
+    expectations: {
+      rand: {
+        noArgs: 8586,
+        minMax: [
+          { max: 100, min: 0, expected: 26 },
+          { max: undefined, min: 0, expected: 8586 },
+          { max: 100, min: undefined, expected: 26, skip: true },
+        ],
+      },
+    },
+  },
+  {
+    seed: 1211,
+    expectations: {
+      rand: {
+        noArgs: 30425,
+        minMax: [
+          { max: 100, min: 0, expected: 92 },
+          { max: undefined, min: 0, expected: 30425 },
+          { max: 100, min: undefined, expected: 92, skip: true },
+        ],
+      },
+    },
+  },
+  {
+    seed: [42, 1, 2],
+    expectations: {
+      rand: {
+        noArgs: 28056,
+        minMax: [
+          { max: 100, min: 0, expected: 85 },
+          { max: undefined, min: 0, expected: 28056 },
+          { max: 100, min: undefined, expected: 85, skip: true },
+        ],
+      },
+    },
+  },
+  {
+    seed: [1337, 1, 2],
+    expectations: {
+      rand: {
+        noArgs: 5895,
+        minMax: [
+          { max: 100, min: 0, expected: 17 },
+          { max: undefined, min: 0, expected: 5895 },
+          { max: 100, min: undefined, expected: 17, skip: true },
+        ],
+      },
+    },
+  },
+  {
+    seed: [1211, 1, 2],
+    expectations: {
+      rand: {
+        noArgs: 29217,
+        minMax: [
+          { max: 100, min: 0, expected: 89 },
+          { max: undefined, min: 0, expected: 29217 },
+          { max: 100, min: undefined, expected: 89, skip: true },
+        ],
+      },
+    },
+  },
+];
+
+const functionNames = ['rand'];
+
+const NON_SEEDED_BASED_RUN = 25;
+
+describe('mersenne twister', () => {
+  let mersenne: Mersenne;
+
+  beforeEach(() => {
+    mersenne = new Mersenne();
+  });
+
+  for (const { seed, expectations } of seededRuns) {
+    describe(`seed: ${JSON.stringify(seed)}`, () => {
+      beforeEach(() => {
+        if (Array.isArray(seed)) {
+          mersenne.seed_array(seed);
+        } else {
+          mersenne.seed(seed);
+        }
+      });
+
+      for (const functionName of functionNames) {
+        it(`${functionName}()`, () => {
+          const actual = mersenne[functionName]();
+
+          expect(actual).toEqual(expectations[functionName].noArgs);
+        });
+      }
+
+      for (const { min, max, expected } of expectations.rand.minMax.filter(
+        (x) => !x.skip
+      )) {
+        it(`should return ${expected} for rand(${max}, ${min})`, () => {
+          const actual = mersenne.rand(max, min);
+
+          expect(actual).toEqual(expected);
+        });
+      }
+
+      // TODO @piotrekn 2022-02-13: There is a bug: https://github.com/faker-js/faker/issues/479
+      // remove minMax.skip when fixed
+      for (const { min, max, expected } of expectations.rand.minMax.filter(
+        (x) => x.skip
+      )) {
+        it.todo(`should return ${expected} for rand(${max}, ${min})`, () => {
+          const actual = mersenne.rand(max, min);
+
+          expect(actual).toEqual(expected);
+        });
+      }
+
+      it.todo(`should return 0 for rand(1)`, () => {
+        const actual = mersenne.rand(1);
+
+        expect(actual).toEqual(0);
+      });
+    });
+  }
+
+  // Create and log-back the seed for debug purposes
+  const seeds = [
+    Math.ceil(Math.random() * 1_000_000_000),
+    [
+      Math.ceil(Math.random() * 1_000_000_000),
+      Math.ceil(Math.random() * 1_000_000_000),
+    ],
+  ];
+
+  for (const seed of seeds) {
+    describe(`random seeded tests ${JSON.stringify(seed)}`, () => {
+      beforeAll(() => {
+        if (Array.isArray(seed)) {
+          mersenne.seed_array(seed);
+        } else {
+          mersenne.seed(seed);
+        }
+      });
+
+      for (let i = 1; i <= NON_SEEDED_BASED_RUN; i++) {
+        describe('rand', () => {
+          it('should return a random number without given min / max arguments', () => {
+            const randomNumber = mersenne.rand();
+            expect(typeof randomNumber).toBe('number');
+          });
+
+          it('should return random number from interval [min, max)', () => {
+            const actual = mersenne.rand(0, 2);
+
+            expect(actual).toBeGreaterThanOrEqual(0);
+            expect(actual).toBeLessThan(2);
+          });
+        });
+      }
+    });
+  }
+
+  it('should throw an error when attempting to seed() a non-integer', () => {
+    expect(() =>
+      mersenne.seed(
+        // @ts-expect-error: non-integer error
+        'abc'
+      )
+    ).toThrowError(Error('seed(S) must take numeric argument; is string'));
+  });
+
+  it('should throw an error when attempting to seed() a non-integer', () => {
+    expect(() =>
+      mersenne.seed_array(
+        // @ts-expect-error: non-integer error
+        'abc'
+      )
+    ).toThrowError(
+      Error('seed_array(A) must take array of numbers; is string')
+    );
+  });
+});

test/random.spec.ts

@@ -252,26 +252,4 @@ describe('random.js', () => {
       spy_console_log.mockRestore();
     });
   });
-
-  describe('mersenne twister', () => {
-    it('returns a random number without given min / max arguments', () => {
-      const randomNumber = mersenne.rand();
-      expect(typeof randomNumber).toBe('number');
-    });
-
-    it('throws an error when attempting to seed() a non-integer', () => {
-      expect(() =>
-        mersenne.seed(
-          // @ts-expect-error
-          'abc'
-        )
-      ).toThrowError(Error('seed(S) must take numeric argument; is string'));
-    });
-
-    it('throws an error when attempting to seed() a non-integer', () => {
-      expect(() => mersenne.seed_array('abc')).toThrowError(
-        Error('seed_array(A) must take array of numbers; is string')
-      );
-    });
-  });
 });