Turn strict_predicate_matchers on by default

Changelog.md

@@ -5,6 +5,7 @@ Breaking Changes:
 
 * Ruby < 2.3 is no longer supported. (Phil Pirozhkov, #1231)
 * Remove `should` and `should_not` syntax (including one-liners). (Phil Pirozhkov, #1245)
+* Turn `strict_predicate_matchers` on by default. (Phil Pirozhkov, #1277)
 
 Enhancements:
 

features/built_in_matchers/predicates.feature

@@ -39,7 +39,7 @@ Feature: Predicate matchers
 
   In either case, RSpec provides nice, clear error messages, such as:
 
-    `expected zero? to be truthy, got false`
+    `expected zero? to return true, got false`
 
   Calling private methods will also fail:
 
@@ -60,7 +60,7 @@ Feature: Predicate matchers
       """
     When I run `rspec be_zero_spec.rb`
     Then the output should contain "2 examples, 1 failure"
-     And the output should contain "expected `7.zero?` to be truthy, got false"
+     And the output should contain "expected `7.zero?` to return true, got false"
 
   Scenario: is_expected.not_to be_empty (based on Array#empty?)
     Given a file named "not_to_be_empty_spec.rb" with:
@@ -75,7 +75,7 @@ Feature: Predicate matchers
       """
     When I run `rspec not_to_be_empty_spec.rb`
     Then the output should contain "2 examples, 1 failure"
-     And the output should contain "expected `[].empty?` to be falsey, got true"
+     And the output should contain "expected `[].empty?` to return false, got true"
 
    Scenario: is_expected.to have_key (based on Hash#has_key?)
     Given a file named "have_key_spec.rb" with:
@@ -88,7 +88,7 @@ Feature: Predicate matchers
       """
     When I run `rspec have_key_spec.rb`
     Then the output should contain "2 examples, 1 failure"
-     And the output should contain "expected `{:foo=>7}.has_key?(:bar)` to be truthy, got false"
+     And the output should contain "expected `{:foo=>7}.has_key?(:bar)` to return true, got false"
 
    Scenario: is_expected.to have_decimals (based on custom #have_decimals? method)
      Given a file named "have_decimals_spec.rb" with:
@@ -114,7 +114,7 @@ Feature: Predicate matchers
        """
      When I run `rspec have_decimals_spec.rb`
      Then the output should contain "2 examples, 1 failure"
-      And the output should contain "expected `42.0.has_decimals?` to be truthy, got false"
+      And the output should contain "expected `42.0.has_decimals?` to return true, got false"
 
    Scenario: matcher arguments are passed on to the predicate method
      Given a file named "predicate_matcher_argument_spec.rb" with:
@@ -136,8 +136,8 @@ Feature: Predicate matchers
        """
      When I run `rspec predicate_matcher_argument_spec.rb`
      Then the output should contain "4 examples, 2 failures"
-      And the output should contain "expected `12.multiple_of?(4)` to be falsey, got true"
-      And the output should contain "expected `12.multiple_of?(5)` to be truthy, got false"
+      And the output should contain "expected `12.multiple_of?(4)` to return false, got true"
+      And the output should contain "expected `12.multiple_of?(5)` to return true, got false"
 
     Scenario: the config `strict_predicate_matchers` impacts matching of results other than `true` and `false`
       Given a file named "strict_or_not.rb" with:
@@ -159,14 +159,14 @@ Feature: Predicate matchers
             end
           end
 
-          context 'with non-strict matchers (default)' do
-            let(:strict) { false }
+          context 'with strict matchers (default)' do
+            let(:strict) { true }
+            # deliberate failure
             it { is_expected.to have_strange_result }
           end
 
-          context 'with strict matchers' do
-            let(:strict) { true }
-            # deliberate failure
+          context 'with non-strict matchers' do
+            let(:strict) { false }
             it { is_expected.to have_strange_result }
           end
         end

features/test_frameworks/minitest.feature

@@ -47,7 +47,7 @@ Feature: Minitest integration
       """
      When I run `ruby rspec_expectations_test.rb`
      Then the output should contain "4 runs, 5 assertions, 2 failures, 0 errors"
-      And the output should contain "expected `[1, 2].empty?` to be truthy, got false"
+      And the output should contain "expected `[1, 2].empty?` to return true, got false"
       And the output should contain "be_an_int is deprecated"
       And the output should contain "Got 2 failures from failure aggregation block"
 
@@ -105,7 +105,7 @@ Feature: Minitest integration
       """
      When I run `ruby rspec_expectations_spec.rb`
      Then the output should contain "9 runs, 10 assertions, 5 failures, 0 errors"
-      And the output should contain "expected `[1, 2].empty?` to be truthy, got false"
+      And the output should contain "expected `[1, 2].empty?` to return true, got false"
       And the output should contain "expected ZeroDivisionError but nothing was raised"
       And the output should contain "Got 2 failures from failure aggregation block"
       And the output should contain "Expected [1, 2] to be empty?"

lib/rspec/expectations/configuration.rb

@@ -26,7 +26,7 @@ class Configuration
 
       def initialize
         @on_potential_false_positives = :warn
-        @strict_predicate_matchers = false
+        @strict_predicate_matchers = true
       end
 
       # Configures the maximum character length that RSpec will print while
@@ -126,9 +126,9 @@ def on_potential_false_positives=(behavior)
         @on_potential_false_positives = behavior
       end
 
-      # Configures RSpec to check predicate matchers to `be(true)` / `be(false)` (strict),
-      # or `be_truthy` / `be_falsey` (not strict).
-      # Historically, the default was `false`, but `true` is recommended.
+      # Configures RSpec to check the values returned by predicate matchers
+      # to be exactly true/false (strict), or truthy/falsey (not strict).
+      # Before RSpec 4, the default was `false`.
       def strict_predicate_matchers=(flag)
         raise ArgumentError, "Pass `true` or `false`" unless flag == true || flag == false
         @strict_predicate_matchers = flag

spec/rspec/expectations/configuration_spec.rb

@@ -61,6 +61,23 @@ class << rspec_dup; undef configuration; end
         end
       end
 
+      describe "#strict_predicate_matchers?" do
+        it "is true by default" do
+          expect(config.strict_predicate_matchers?).to be(true)
+        end
+
+        it "can be set to false" do
+          config.strict_predicate_matchers = false
+          expect(config.strict_predicate_matchers?).to be(false)
+        end
+
+        it "can be set back to true" do
+          config.strict_predicate_matchers = false
+          config.strict_predicate_matchers = true
+          expect(config.strict_predicate_matchers?).to be(true)
+        end
+      end
+
       describe "#max_formatted_output_length=" do
         before do
           @orig_max_formatted_output_length = RSpec::Support::ObjectFormatter.default_instance.max_formatted_output_length

spec/rspec/matchers/built_in/has_spec.rb

@@ -131,7 +131,7 @@ def o.has_sym?(sym); sym == :foo; end
     expect({ :a => "A" }).not_to have_key(:b)
   end
 
-  context "when strict_predicate_matchers is set to true" do
+  context "when strict_predicate_matchers is set to true", with_configuration: {strict_predicate_matchers: true} do
     it "fails when #has_sym? returns nil" do
       actual = double("actual", :has_foo? => nil)
       expect {
@@ -140,13 +140,7 @@ def o.has_sym?(sym); sym == :foo; end
     end
   end
 
-  context "when strict_predicate_matchers is set to false" do
-    around do |example|
-      RSpec::Expectations.configuration.strict_predicate_matchers = false
-      example.run
-      RSpec::Expectations.configuration.strict_predicate_matchers = true
-    end
-
+  context "when strict_predicate_matchers is set to false", with_configuration: {strict_predicate_matchers: false} do
     it "passes if #has_sym?(*args) returns nil" do
       actual = double("actual", :has_foo? => nil)
       expect(actual).not_to have_foo

spec/spec_helper.rb

@@ -40,7 +40,6 @@ def hash_inspect(hash)
 
   config.expect_with :rspec do |expectations|
     expectations.include_chain_clauses_in_custom_matcher_descriptions = true
-    expectations.strict_predicate_matchers = true
   end
 
   config.mock_with :rspec do |mocks|
@@ -70,6 +69,23 @@ def hash_inspect(hash)
 end
 RSpec.configuration.include_context "with warn_about_potential_false_positives set to false", :warn_about_potential_false_positives
 
+RSpec.shared_context "with modified configuration" do
+  around do |example|
+    configuration = example.metadata[:with_configuration]
+    original = configuration.keys.each.with_object({}) do |key, config|
+      config[key] = RSpec::Expectations.configuration.public_send(key)
+    end
+    configuration.each do |key, value|
+      RSpec::Expectations.configuration.public_send("#{key}=", value)
+    end
+    example.run
+    original.each do |key, value|
+      RSpec::Expectations.configuration.public_send("#{key}=", value)
+    end
+  end
+end
+RSpec.configuration.include_context "with modified configuration", :with_configuration
+
 module MinitestIntegration
   include ::RSpec::Support::InSubProcess