Fixed CLI crashing after gem install

Gemfile

@@ -11,7 +11,6 @@ gem "rubocop", "~> 1.21"
 gem "rubocop-performance"
 gem "rubocop-rake"
 gem "rubocop-rspec"
-gem "tty-table"
 
 # Optional dependencies — loaded lazily by the feature that needs them.
 group :optional do

dcc.gemspec

@@ -40,4 +40,5 @@ Gem::Specification.new do |spec|
   spec.add_dependency "mml", "~> 2.4.0"
   spec.add_dependency "moxml", "~> 0.1.26"
   spec.add_dependency "thor"
+  spec.add_dependency "tty-table"
 end

lib/dcc/cli/cli.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "thor"
-require "tty-table"
 
 # `Dcc::Cli::Cli` is the Thor-based command-line interface. Each subcommand
 # (validate, convert, extract, signature, transform, inspect, diff, issue)

spec/dcc/cli/dependencies_spec.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+# The CLI ships as `exe/dcc`. Every gem it requires at load time must be a
+# declared runtime dependency, or `gem install dcc` yields a binary that
+# crashes on every command.
+# rubocop:disable RSpec/DescribeClass -- packaging invariant, not a class
+RSpec.describe "dcc CLI runtime dependencies" do
+  let(:root) { File.expand_path("../../..", __dir__) }
+  let(:gemspec) { Gem::Specification.load(File.join(root, "dcc.gemspec")) }
+  let(:declared) { gemspec.runtime_dependencies.map(&:name) }
+  let(:stdlib) do
+    %w[base64 bigdecimal csv date digest json open3 openssl set stringio yaml]
+  end
+
+  # Matches indented requires (inside a method or conditional) and both quote
+  # styles. Does not match parenthesized, multiline, or interpolated requires
+  # -- add one of those and this guard will not see it.
+  let(:required) do
+    pattern = /^\s*require ["']([^"']+)["']/
+    Dir[File.join(root, "lib", "dcc", "cli", "**", "*.rb")]
+      .flat_map { |f| File.read(f).scan(pattern).flatten }
+      .reject { |name| name.start_with?("dcc/") }
+      .map { |name| name.split("/").first }
+      .uniq - stdlib
+  end
+
+  it "finds the gems the CLI requires" do
+    expect(required).to include("thor", "tty-table")
+  end
+
+  it "declares every third-party gem the CLI requires" do
+    expect(required - declared).to be_empty
+  end
+end
+# rubocop:enable RSpec/DescribeClass