```ruby
require "spec_helper"
require "minitest_to_rspec/cli"

module MinitestToRspec
  RSpec.describe CLI do
    describe ".new" do
      context "target omitted" do
        it "infers target" do
          argv = ["test/fruit/banana_test.rb"]
          cli = described_class.new(argv)
          expect(cli.target).to eq("spec/fruit/banana_spec.rb")
        end
      end
    end
  end
end
```

Complete test coverage of CLI
user
```ruby
require "spec_helper"
require "minitest_to_rspec/cli"

module MinitestToRspec
  RSpec.describe CLI do
    let(:cli) { described_class.new([source, target]) }
    let(:source) { "spec/fixtures/01_trivial_assertion/in.rb" }
    let(:target) { "/dev/null" }

    describe ".new" do
      context "target omitted" do
        it "infers target" do
          cli = described_class.new(["test/fruit/banana_test.rb"])
          expect(cli.target).to eq("spec/fruit/banana_spec.rb")
        end
      end

      context "no arguments" do
        it "educates the user" do
          expect {
            expect { described_class.new([]) }.to output(/Usage/).to_stderr
          }.to raise_error(SystemExit)
        end
      end
    end

    describe "#run" do
      it "converts source to target" do
        expect(cli).to receive(:assert_file_does_not_exist)
        cli.run
      end

      it "catches MinitestToRspec::Error" do
        allow(cli).to receive(:assert_file_does_not_exist)
        allow(cli).to receive(:converter).and_raise(Error, "so sad")
        expect {
          expect { cli.run }.to output("Failed to convert: so sad").to_stderr
        }.to raise_error(SystemExit)
      end
    end

    describe "#assert_file_does_not_exist" do
      context "when file exists" do
        it "exits with code E_FILE_ALREADY_EXISTS" do
          expect {
            expect { cli.run }.to output(
              "File already exists: /dev/null"
            ).to_stderr
          }.to raise_error(SystemExit)
        end
      end
    end

    describe "#assert_file_exists" do
      context "when file does not exist" do
        let(:source) { "does_not_exist_3819e90182546cf5da27f193d0f3000164" }

        it "exits with code E_FILE_NOT_FOUND" do
          expect {
            expect { cli.run }.to output(
              "File not found: #{source}"
            ).to_stderr
          }.to raise_error(SystemExit)
        end
      end
    end
  end
end
```
assistant