Testing ErrorPage Component Integration in BetterErrors
This test suite examines the ErrorPage functionality in BetterErrors, focusing on error display, variable inspection, and REPL integration. It verifies error message rendering, variable binding handling, and interactive debugging features across different runtime environments.
Test Coverage Overview
Implementation Analysis
Technical Details
Best Practices Demonstrated
bettererrors/better_errors
spec/better_errors/error_page_spec.rb
require "spec_helper"
class ErrorPageTestIgnoredClass; end
module BetterErrors
describe ErrorPage do
# It's necessary to use HTML matchers here that are specific as possible.
# This is because if there's an exception within this file, the lines of code will be reflected in the
# generated HTML, so any strings being matched against the HTML content will be there if they're within 5
# lines of code of the exception that was raised.
let!(:exception) { raise ZeroDivisionError, "you divided by zero you silly goose!" rescue $! }
let(:error_page) { ErrorPage.new exception, { "PATH_INFO" => "/some/path" } }
let(:response) { error_page.render_main("CSRF_TOKEN", "CSP_NONCE") }
let(:exception_binding) {
local_a = :value_for_local_a
local_b = :value_for_local_b
@inst_c = :value_for_inst_c
@inst_d = :value_for_inst_d
binding
}
it "includes the error message" do
expect(response).to have_tag('.exception p', text: /you divided by zero you silly goose!/)
end
it "includes the request path" do
expect(response).to have_tag('.exception h2', %r{/some/path})
end
it "includes the exception class" do
expect(response).to have_tag('.exception h2', /ZeroDivisionError/)
end
context 'when ActiveSupport::ActionableError is available' do
before do
skip "ActiveSupport missing on this platform" unless Object.constants.include?(:ActiveSupport)
skip "ActionableError missing on this platform" unless ActiveSupport.constants.include?(:ActionableError)
end
context 'when ActiveSupport provides one or more actions for this error type' do
let(:exception_class) {
Class.new(StandardError) do
include ActiveSupport::ActionableError
action "Do a thing" do
puts "Did a thing"
end
end
}
let(:exception) { exception_binding.eval("raise exception_class") rescue $! }
it "includes a fix-action form for each action" do
expect(response).to have_tag('.fix-actions') do
with_tag('form.button_to')
with_tag('form.button_to input[type=submit][value="Do a thing"]')
end
end
end
context 'when ActiveSupport does not provide any actions for this error type' do
let(:exception_class) {
Class.new(StandardError)
}
let(:exception) { exception_binding.eval("raise exception_class") rescue $! }
it "does not include a fix-action form" do
expect(response).not_to have_tag('.fix-actions')
end
end
end
context "variable inspection" do
let(:html) { error_page.do_variables("index" => 0)[:html] }
let(:exception) { exception_binding.eval("raise") rescue $! }
it 'includes an editor link for the full path of the current frame' do
expect(html).to have_tag('.location .filename') do
with_tag('a[href*="better_errors"]')
end
end
context 'when BETTER_ERRORS_INSIDE_FRAME is set in the environment' do
before do
ENV['BETTER_ERRORS_INSIDE_FRAME'] = '1'
end
after do
ENV['BETTER_ERRORS_INSIDE_FRAME'] = nil
end
it 'includes an editor link with target=_blank' do
expect(html).to have_tag('.location .filename') do
with_tag('a[href*="better_errors"][target="_blank"]')
end
end
end
context 'when BETTER_ERRORS_INSIDE_FRAME is not set in the environment' do
it 'includes an editor link without target=_blank' do
expect(html).to have_tag('.location .filename') do
with_tag('a[href*="better_errors"]:not([target="_blank"])')
end
end
end
context "when binding_of_caller is loaded" do
before do
skip "binding_of_caller is not loaded" unless BetterErrors.binding_of_caller_available?
end
it "shows local variables" do
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: 'local_a')
with_tag('pre', text: ':value_for_local_a')
end
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: 'local_b')
with_tag('pre', text: ':value_for_local_b')
end
end
it "shows instance variables" do
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: '@inst_c')
with_tag('pre', text: ':value_for_inst_c')
end
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: '@inst_d')
with_tag('pre', text: ':value_for_inst_d')
end
end
context 'when ignored_classes includes the class name of a local variable' do
before do
allow(BetterErrors).to receive(:ignored_classes).and_return(['ErrorPageTestIgnoredClass'])
end
let(:exception_binding) {
local_a = :value_for_local_a
local_b = ErrorPageTestIgnoredClass.new
@inst_c = :value_for_inst_c
@inst_d = ErrorPageTestIgnoredClass.new
binding
}
it "does not include that value" do
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: 'local_a')
with_tag('pre', text: ':value_for_local_a')
end
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: 'local_b')
with_tag('.unsupported', text: /Instance of ignored class/)
with_tag('.unsupported', text: /BetterErrors\.ignored_classes/)
end
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: '@inst_c')
with_tag('pre', text: ':value_for_inst_c')
end
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: '@inst_d')
with_tag('.unsupported', text: /Instance of ignored class/)
with_tag('.unsupported', text: /BetterErrors\.ignored_classes/)
end
end
end
it "does not show filtered variables" do
allow(BetterErrors).to receive(:ignored_instance_variables).and_return([:@inst_d])
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: '@inst_c')
with_tag('pre', text: ':value_for_inst_c')
end
expect(html).not_to have_tag('div.variables td.name', text: '@inst_d')
end
context 'when maximum_variable_inspect_size is set' do
before do
BetterErrors.maximum_variable_inspect_size = 1010
end
context 'on a platform with ObjectSpace' do
before do
skip "Missing on this platform" unless Object.constants.include?(:ObjectSpace)
end
context 'with a variable that is smaller than maximum_variable_inspect_size' do
let(:exception_binding) {
@small = content
binding
}
let(:content) { 'A' * 480 }
it "shows the variable content" do
expect(html).to have_tag('div.variables', text: %r{#{content}})
end
end
context 'with a variable that is larger than maximum_variable_inspect_size' do
context 'but has an #inspect that returns a smaller value' do
let(:exception_binding) {
@big = content
binding
}
let(:content) {
class ExtremelyLargeInspectableTestValue
def initialize
@a = 'A' * 1101
end
def inspect
"shortval"
end
end
ExtremelyLargeInspectableTestValue.new
}
it "shows the variable content" do
expect(html).to have_tag('div.variables', text: /shortval/)
end
end
context 'and does not implement #inspect' do
let(:exception_binding) {
@big = content
binding
}
let(:content) { 'A' * 1101 }
it "includes an indication that the variable was too large" do
expect(html).not_to have_tag('div.variables', text: %r{#{content}})
expect(html).to have_tag('div.variables', text: /Object too large/)
end
end
context "when the variable's class is anonymous" do
let(:exception_binding) {
@big_anonymous = Class.new do
def initialize
@content = 'A' * 1101
end
end.new
binding
}
it "does not attempt to show the class name" do
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: '@big_anonymous')
with_tag('.unsupported', text: /Object too large/)
with_tag('.unsupported', text: /Adjust BetterErrors.maximum_variable_inspect_size/)
end
end
end
end
end
context 'on a platform without ObjectSpace' do
before do
Object.send(:remove_const, :ObjectSpace) if Object.constants.include?(:ObjectSpace)
end
after do
require "objspace" rescue nil
end
context 'with a variable that is smaller than maximum_variable_inspect_size' do
let(:exception_binding) {
@small = content
binding
}
let(:content) { 'A' * 480 }
it "shows the variable content" do
expect(html).to have_tag('div.variables', text: %r{#{content}})
end
end
context 'with a variable that is larger than maximum_variable_inspect_size' do
context 'but has an #inspect that returns a smaller value' do
let(:exception_binding) {
@big = content
binding
}
let(:content) {
class ExtremelyLargeInspectableTestValue
def initialize
@a = 'A' * 1101
end
def inspect
"shortval"
end
end
ExtremelyLargeInspectableTestValue.new
}
it "shows the variable content" do
expect(html).to have_tag('div.variables', text: /shortval/)
end
end
context 'and does not implement #inspect' do
let(:exception_binding) {
@big = content
binding
}
let(:content) { 'A' * 1101 }
it "includes an indication that the variable was too large" do
expect(html).not_to have_tag('div.variables', text: %r{#{content}})
expect(html).to have_tag('div.variables', text: /Object too large/)
end
end
end
context "when the variable's class is anonymous" do
let(:exception_binding) {
@big_anonymous = Class.new do
def initialize
@content = 'A' * 1101
end
end.new
binding
}
it "does not attempt to show the class name" do
expect(html).to have_tag('div.variables tr') do
with_tag('td.name', text: '@big_anonymous')
with_tag('.unsupported', text: /Object too large/)
with_tag('.unsupported', text: /Adjust BetterErrors.maximum_variable_inspect_size/)
end
end
end
end
end
context 'when maximum_variable_inspect_size is disabled' do
before do
BetterErrors.maximum_variable_inspect_size = nil
end
let(:exception_binding) {
@big = content
binding
}
let(:content) { 'A' * 100_001 }
it "includes the content of large variables" do
expect(html).to have_tag('div.variables', text: %r{#{content}})
expect(html).not_to have_tag('div.variables', text: /Object too large/)
end
end
end
context "when binding_of_caller is not loaded" do
before do
skip "binding_of_caller is loaded" if BetterErrors.binding_of_caller_available?
end
it "tells the user to add binding_of_caller to their gemfile to get fancy features" do
expect(html).not_to have_tag('div.variables', text: /gem "binding_of_caller"/)
end
end
end
it "doesn't die if the source file is not a real filename" do
allow(exception).to receive(:__better_errors_bindings_stack).and_return([])
allow(exception).to receive(:backtrace).and_return([
"<internal:prelude>:10:in `spawn_rack_application'"
])
expect(response).to have_tag('.frames li .location .filename', text: '<internal:prelude>')
end
context 'with an exception with blank lines' do
class SpacedError < StandardError
def initialize(message = nil)
message = "\n\n#{message}" if message
super
end
end
let!(:exception) { raise SpacedError, "Danger Warning!" rescue $! }
it 'does not include leading blank lines in exception_message' do
expect(exception.message).to match(/\A\n\n/)
expect(error_page.exception_message).not_to match(/\A\n\n/)
end
end
describe '#do_eval' do
let(:exception) { exception_binding.eval("raise") rescue $! }
subject(:do_eval) { error_page.do_eval("index" => 0, "source" => command) }
let(:command) { 'EvalTester.stuff_was_done(:yep)' }
before do
stub_const('EvalTester', eval_tester)
end
let(:eval_tester) { double('EvalTester', stuff_was_done: 'response') }
context 'without binding_of_caller' do
before do
skip("Disabled with binding_of_caller") if defined? ::BindingOfCaller
end
it "does not evaluate the code" do
do_eval
expect(eval_tester).to_not have_received(:stuff_was_done).with(:yep)
end
it 'returns an error indicating no REPL' do
expect(do_eval).to include(
error: "REPL unavailable in this stack frame",
)
end
end
context 'with binding_of_caller available' do
before do
skip("Disabled without binding_of_caller") unless defined? ::BindingOfCaller
end
context 'with Pry disabled or unavailable' do
it "evaluates the code" do
do_eval
expect(eval_tester).to have_received(:stuff_was_done).with(:yep)
end
it 'returns a hash of the code and its result' do
expect(do_eval).to include(
highlighted_input: /stuff_was_done/,
prefilled_input: '',
prompt: '>>',
result: "=> \"response\"\n",
)
end
end
context 'with Pry enabled' do
before do
skip("Disabled without pry") unless defined? ::Pry
BetterErrors.use_pry!
# Cause the provider to be unselected, so that it will be re-detected.
BetterErrors::REPL.provider = nil
end
after do
BetterErrors::REPL::PROVIDERS.shift
BetterErrors::REPL.provider = nil
# Ensure the Pry REPL file has not been included. If this is not done,
# the constant leaks into other examples.
BetterErrors::REPL.send(:remove_const, :Pry)
end
it "evaluates the code" do
BetterErrors::REPL.provider
do_eval
expect(eval_tester).to have_received(:stuff_was_done).with(:yep)
end
it 'returns a hash of the code and its result' do
expect(do_eval).to include(
highlighted_input: /stuff_was_done/,
prefilled_input: '',
prompt: '>>',
result: "=> \"response\"\n",
)
end
end
end
end
end
end