first_duplicate_test.rb

require_relative "../../test_helper"
require_relative "first_duplicate"

describe FirstDuplicate do
  describe "edge cases" do
    it "should return -1 when input is empty" do
      actual = FirstDuplicate.run([], target: 3)
      expect(actual).must_equal(-1)
    end

    it "should return -1 when input is nil" do
      actual = FirstDuplicate.run(nil, target: 3)
      expect(actual).must_equal(-1)
    end
  end

  describe "base cases" do
    it "should return -1 for single element in array not equal to target" do
      actual = FirstDuplicate.run([0], target: 1)
      expect(actual).must_equal(-1)
    end

    it "should return 0 for single element in array equal to target" do
      actual = FirstDuplicate.run([1], target: 1)
      expect(actual).must_equal 0
    end
  end

  describe "regular cases" do
    it "should return first index when all elements are the same" do
      actual = FirstDuplicate.run([1, 1, 1, 1, 1, 1], target: 1)
      expect(actual).must_equal 0
    end

    it "should return -1 when array has no dupes" do
      actual = FirstDuplicate.run([0, 1, 2, 3, 4, 5], target: 6)
      expect(actual).must_equal(-1)
    end

    it "should find first dupe" do
      actual = FirstDuplicate.run([0, 1, 2, 6, 6, 7, 8, 9], target: 6)
      expect(actual).must_equal 3
    end

    it "should find first dupe towards front of array" do
      actual = FirstDuplicate.run([0, 0, 2, 6, 6, 7, 8, 9], target: 0)
      expect(actual).must_equal 0
    end

    it "should find first dupe towards back of array" do
      actual = FirstDuplicate.run([1, 2, 3, 4, 5, 6, 7, 8, 8, 9, 9], target: 9)
      expect(actual).must_equal 9
    end
  end
end