stack.test.js

const Stack = require("./stack");

let stack;

beforeEach(function() {
  stack = new Stack();
});

describe("push", function() {
  it("places the value at the top of the stack and returns undefined", function() {
    expect(stack.push(10)).toBe(undefined);
    expect(stack.first.val).toBe(10);
    expect(stack.last.val).toBe(10);
    stack.push(100);
    expect(stack.first.val).toBe(100);
    expect(stack.last.val).toBe(10);
    stack.push(1000);
    expect(stack.first.val).toBe(1000);
    expect(stack.last.val).toBe(10);
  });
});

describe("pop", function() {
  it("returns the value of the node removed", function() {
    stack.push(10);
    stack.push(100);
    stack.push(1000);
    var removed = stack.pop();
    expect(removed).toBe(1000);
    expect(stack.size).toBe(2);
    stack.pop();
    stack.pop();
    expect(stack.size).toBe(0);
  });

  it("throws an error if the stack is empty", function() {
    expect(() => stack.pop()).toThrow(Error);
  });
});

describe("peek", function() {
  it("returns the value at the start of the stack", function() {
    stack.push(3);
    expect(stack.peek()).toBe(3);
    stack.push(5);
    expect(stack.peek()).toBe(5);
  });
});

describe("isEmpty", function() {
  it("returns true for empty stacks", function() {
    expect(stack.isEmpty()).toBe(true);
  });

  it("returns false for nonempty stacks", function() {
    stack.push(3);
    expect(stack.isEmpty()).toBe(false);
  });
});

// PASS  ./stack.test.js
// push
//   ✓ places the value at the top of the stack and returns undefined (1ms)
// pop
//   ✓ returns the value of the node removed (1ms)
//   ✓ throws an error if the stack is empty (1ms)
// peek
//   ✓ returns the value at the start of the stack (1ms)
// isEmpty
//   ✓ returns true for empty stacks
//   ✓ returns false for nonempty stacks

// Test Suites: 1 passed, 1 total
// Tests:       6 passed, 6 total
// Snapshots:   0 total
// Time:        0.617s, estimated 1s
// Ran all test suites matching /stack.test.js/i.