array_peak_test.rb

require_relative "../../test_helper"
require_relative "array_peak"

describe ArrayPeak do
  describe "corner cases" do
    it "should return nil for empty array as input" do
      actual = ArrayPeak.run([])
      expect(actual).must_be_nil
    end

    it "should work for array with single item" do
      actual = ArrayPeak.run([1])
      expect(actual).must_equal 1
    end

    it "should work for array with 2 asc elements" do
      actual = ArrayPeak.run([0, 1])
      expect(actual).must_equal 1
    end

    it "should work for array with 2 desc elements" do
      actual = ArrayPeak.run([1, 0])
      expect(actual).must_equal 1
    end

    it "should work when first element is peak" do
      actual = ArrayPeak.run([5, 3, 1])
      expect(actual).must_equal 5
    end

    it "should work when last element is peak" do
      actual = ArrayPeak.run([1, 2, 3])
      expect(actual).must_equal 3
    end
  end

  describe "regular cases" do
    it "should find the peak in the middle" do
      actual = ArrayPeak.run([5, 10, 20, 15, 16, 17, 18, 15])
      expect(actual).must_equal 20
    end
  end
end