[rubygems/rubygems] Make slow perf specs more stable

This seems worse to detect performance regressions, but at least should
not have many false positives.

https://github.com/rubygems/rubygems/commit/0b28e55415

spec/bundler/realworld/slow_perf_spec.rb

@@ -11,7 +11,8 @@ RSpec.describe "bundle install with complex dependencies", realworld: true do
       gem "mongoid", ">= 0.10.2"
     G
 
-    expect { bundle "lock" }.to take_less_than(18) # seconds
+    bundle "lock", env: { "DEBUG_RESOLVER" => "1" }
+    expect(out).to include("Solution found after 1 attempts")
   end
 
   it "resolves quickly (case 2)" do
@@ -28,7 +29,8 @@ RSpec.describe "bundle install with complex dependencies", realworld: true do
       gem 'rspec-rails'
     G
 
-    expect { bundle "lock" }.to take_less_than(30) # seconds
+    bundle "lock", env: { "DEBUG_RESOLVER" => "1" }
+    expect(out).to include("Solution found after 1 attempts")
   end
 
   it "resolves big gemfile quickly" do
@@ -129,8 +131,14 @@ RSpec.describe "bundle install with complex dependencies", realworld: true do
       end
     G
 
-    expect do
-      bundle "lock", env: { "DEBUG_RESOLVER" => "1" }, raise_on_error: !Bundler.feature_flag.bundler_3_mode?
-    end.to take_less_than(30) # seconds
+    if Bundler.feature_flag.bundler_3_mode?
+      bundle "lock", env: { "DEBUG_RESOLVER" => "1" }, raise_on_error: false
+
+      expect(out).to include("backtracking").exactly(26).times
+    else
+      bundle "lock", env: { "DEBUG_RESOLVER" => "1" }
+
+      expect(out).to include("Solution found after 10 attempts")
+    end
   end
 end

spec/bundler/support/matchers.rb

@@ -97,32 +97,6 @@ module Spec
       end
     end
 
-    RSpec::Matchers.define :take_less_than do |seconds|
-      match do |actual|
-        start_time = Time.now
-
-        actual.call
-
-        actual_time = (Time.now - start_time).to_f
-
-        acceptable = actual_time < seconds
-
-        @errors = ["took #{actual_time} seconds"] unless acceptable
-
-        acceptable
-      end
-
-      failure_message do
-        super() + " but:\n" + @errors.map {|e| indent(e) }.join("\n")
-      end
-
-      failure_message_when_negated do
-        super() + " but:\n" + @errors.map {|e| indent(e) }.join("\n")
-      end
-
-      supports_block_expectations
-    end
-
     define_compound_matcher :read_as, [exist] do |file_contents|
       diffable