add some tests for RubyAlgebra::Parser

Rakefile

@@ -1,4 +1,7 @@
 # frozen_string_literal: true
 
 require "bundler/gem_tasks"
+require "rspec/core/rake_task"
+
+RSpec::Core::RakeTask.new(:spec)
 task default: %i[]

ruby_algebra.gemspec

@@ -35,6 +35,8 @@ Gem::Specification.new do |spec|
 
   # Uncomment to register a new dependency of your gem
   # spec.add_dependency "example-gem", "~> 1.0"
+  #
+  spec.add_development_dependency "rspec", "~> 3.13"
 
   # For more information and examples about making a new gem, check out our
   # guide at: https://bundler.io/guides/creating_gem.html

spec/parser_spec.rb

@@ -0,0 +1,67 @@
+require "ruby_algebra"
+
+RSpec.configure do |config|
+  config.expect_with :rspec do |expectations|
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+end
+
+RSpec.describe RubyAlgebra::Parser do
+  describe "#parse" do
+    it "returns nil for an empty string" do
+      expect(RubyAlgebra::Parser.parse("")).to eq nil
+    end
+
+    it "returns Constant(a) for a" do
+      [10, 100, 343843, 180.1, 777, 0.52242].each do |a|
+        expect(RubyAlgebra::Parser.parse(a.to_s)).to eq RubyAlgebra::Constant.new(a)
+      end
+    end
+
+    it "returns Variable(x) for x" do
+      ["x", "y", "z", "coolVariable"].each do |x|
+        expect(RubyAlgebra::Parser.parse(x)).to eq RubyAlgebra::Variable.new(x)
+      end
+    end
+
+    it "returns Addition(Constant(5), Variable(x)) for 5 + x" do
+      expect(RubyAlgebra::Parser.parse("5 + x")).to eq RubyAlgebra::Addition.new(RubyAlgebra::Constant.new(5), RubyAlgebra::Variable.new("x"))
+    end
+
+    it "returns Subtraction(Variable(z), Variable(h)) for z - h" do
+      expect(RubyAlgebra::Parser.parse("z - h")).to eq RubyAlgebra::Subtraction.new(RubyAlgebra::Variable.new("z"), RubyAlgebra::Variable.new("h"))
+    end
+
+    it "returns Multiplication(Constant(5), Constant(8)) for 60 * 8" do
+      expect(RubyAlgebra::Parser.parse("60 * 8")).to eq RubyAlgebra::Multiplication.new(RubyAlgebra::Constant.new(60), RubyAlgebra::Constant.new(8))
+    end
+
+    it "returns Division(Constant(3), Variable(j)) for 3/j" do
+      expect(RubyAlgebra::Parser.parse("3/j")).to eq RubyAlgebra::Division.new(RubyAlgebra::Constant.new(3), RubyAlgebra::Variable.new("j"))
+    end
+
+    it "returns Division(Constant(3), Variable(j)) for 3/j" do
+      expect(RubyAlgebra::Parser.parse("3/j")).to eq RubyAlgebra::Division.new(RubyAlgebra::Constant.new(3), RubyAlgebra::Variable.new("j"))
+    end
+
+    it "returns Power(Constant(2), Constant(24)) for 2^24" do
+      expect(RubyAlgebra::Parser.parse("2^24")).to eq RubyAlgebra::Power.new(RubyAlgebra::Constant.new(2), RubyAlgebra::Constant.new(24))
+    end
+
+    it "returns Multiplication(Constant(-1), Variable(x)) for -x" do
+      expect(RubyAlgebra::Parser.parse("-x")).to eq RubyAlgebra::Multiplication.new(RubyAlgebra::Constant.new(-1), RubyAlgebra::Variable.new("x"))
+    end
+
+    it "returns Variable(x) for +x" do
+      expect(RubyAlgebra::Parser.parse("x")).to eq RubyAlgebra::Variable.new("x")
+    end
+
+    it "returns Addition(Addition(Constant(3), Constant(30)), Constant(300)) for 3 + 30 + 300" do
+      expect(RubyAlgebra::Parser.parse("3 + 30 + 300")).to eq RubyAlgebra::Addition.new(RubyAlgebra::Addition.new(RubyAlgebra::Constant.new(3), RubyAlgebra::Constant.new(30)), RubyAlgebra::Constant.new(300))
+    end
+
+    it "returns Power(Constant(10), Power(Constant(10), Constant(10))) for 10 ^ 10 ^ 10" do
+      expect(RubyAlgebra::Parser.parse("10 ^ 10 ^ 10")).to eq RubyAlgebra::Power.new(RubyAlgebra::Constant.new(10), RubyAlgebra::Power.new(RubyAlgebra::Constant.new(10), RubyAlgebra::Constant.new(10)))
+    end
+  end
+end