RSpec "Failure/Error: Unable to find matching line from backtrace" On every test - ruby

Question

I am working through some Ruby problem sets. I'm using Ubuntu 14.04, rbenv 0.4.0-98-g13a474c, rspec 3.1.4, and ruby 2.0.0p353. I'm running into the following errors for every test I run and I'm hoping someone might be able to guide me in the right direction to a solution.
I have run rspec tests successfully in the past but I can't seem to figure out the issue with my current setup.
Here is the message I receive for every test I run:
6) age is an integer
Failure/Error: Unable to find matching line from backtrace
ArgumentError:
wrong number of arguments (0 for 1)
# /usr/lib/ruby/vendor_ruby/rspec/mocks.rb:10:in `setup'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/mocking_adapters/rspec.rb:19:in `setup_mocks_for_rspec'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example.rb:366:in `run_before_example'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example.rb:150:in `block in run'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example.rb:328:in `with_around_example_hooks'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example.rb:148:in `run'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example_group.rb:500:in `block in run_examples'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example_group.rb:496:in `map'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example_group.rb:496:in `run_examples'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/example_group.rb:463:in `run'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/runner.rb:111:in `block (2 levels) in run_specs'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/runner.rb:111:in `map'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/runner.rb:111:in `block in run_specs'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/reporter.rb:53:in `report'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/runner.rb:107:in `run_specs'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/runner.rb:85:in `run'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/runner.rb:69:in `run'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/lib/rspec/core/runner.rb:37:in `invoke'
# /var/lib/gems/1.9.1/gems/rspec-core-3.1.4/exe/rspec:4:in `<top (required)>'
# /usr/local/bin/rspec:23:in `load'
# /usr/local/bin/rspec:23:in `<main>'
#
# Showing full backtrace because every line was filtered out.
# See docs for RSpec::Configuration#backtrace_exclusion_patterns and
# RSpec::Configuration#backtrace_inclusion_patterns for more information.
Edit: Here is an example of one of the spec files, however, the issue comes up on about 20 spec files. I know my solutions are correct and my peers aren't having the same issues I am:
first_name = "M"
last_name = "R"
age = 23
describe 'first_name' do
it "is defined as a local variable" do
expect(defined?(first_name)).to eq 'local-variable'
end
it "is a String" do
expect(first_name).to be_a String
end
end
describe 'last_name' do
it "is defined as a local variable" do
expect(defined?(last_name)).to eq 'local-variable'
end
it "be a String" do
expect(last_name).to be_a String
end
end
describe 'age' do
it "is defined as a local variable" do
expect(defined?(age)).to eq 'local-variable'
end
it "is an integer" do
expect(age).to be_a Fixnum
end
end