Add tests for fib[], fib.terms method
user
```ruby
require 'minitest/autorun'
require 'fibonacci'

class FibonacciTest < MiniTest::Unit::TestCase
  def setup
    @fib = Fibonacci.new
  end

  def test_brackets_method
    assert_equal 0, @fib[0]
    assert_equal 1, @fib[1]
    assert_equal 34, @fib[9]
    assert_equal 55, @fib[10]
    assert_equal 354224848179261915075, @fib[100]

    assert_raises ArgumentError do
      @fib[-1]
    end

    assert_raises ArgumentError do
      @fib["12"]
    end

    assert_raises ArgumentError do
      @fib[1.0]
    end
  end

  def test_terms
    assert_equal [0, 1, 1, 2, 3, 5], @fib.terms(6)
    assert_equal [], @fib.terms(0)
    assert_equal [0], @fib.terms(1)

    assert_raises ArgumentError do
      @fib.terms(-1)
    end

    assert_raises TypeError do
      @fib.terms("12")
    end

    assert_raises RangeError do
      @fib.terms(100000000000000000000000000000)
    end
  end
end
```
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