diff --git a/Library/Homebrew/test/ENV_spec.rb b/Library/Homebrew/test/ENV_spec.rb
index 1f0632b12b..c09a50bca6 100644
--- a/Library/Homebrew/test/ENV_spec.rb
+++ b/Library/Homebrew/test/ENV_spec.rb
@@ -11,7 +11,7 @@ describe "ENV" do
 
     it "supports switching compilers" do
       subject.clang
-      expect(subject["LD"]).to be nil
+      expect(subject["LD"]).to be_nil
       expect(subject["CC"]).to eq(subject["OBJC"])
     end
 
@@ -23,7 +23,7 @@ describe "ENV" do
           subject["foo"] = "bar"
         end
 
-        expect(subject["foo"]).to be nil
+        expect(subject["foo"]).to be_nil
         expect(subject).to eq(before)
       end
 
@@ -37,7 +37,7 @@ describe "ENV" do
           end
         }.to raise_error(StandardError)
 
-        expect(subject["foo"]).to be nil
+        expect(subject["foo"]).to be_nil
         expect(subject).to eq(before)
       end
 
@@ -139,7 +139,7 @@ describe "ENV" do
       subject["MAKEFLAGS"] = "-j4"
 
       subject.deparallelize do
-        expect(subject["MAKEFLAGS"]).to be nil
+        expect(subject["MAKEFLAGS"]).to be_nil
       end
 
       expect(subject["MAKEFLAGS"]).to eq("-j4")
diff --git a/Library/Homebrew/test/PATH_spec.rb b/Library/Homebrew/test/PATH_spec.rb
index 68357d4b85..efd7fdfc88 100644
--- a/Library/Homebrew/test/PATH_spec.rb
+++ b/Library/Homebrew/test/PATH_spec.rb
@@ -125,7 +125,7 @@ describe PATH do
     end
 
     it "returns nil instead of an empty #{described_class}" do
-      expect(described_class.new.existing).to be nil
+      expect(described_class.new.existing).to be_nil
     end
   end
 end
diff --git a/Library/Homebrew/test/cask/dsl_spec.rb b/Library/Homebrew/test/cask/dsl_spec.rb
index 97e6caf5c0..f8f3c0ecf7 100644
--- a/Library/Homebrew/test/cask/dsl_spec.rb
+++ b/Library/Homebrew/test/cask/dsl_spec.rb
@@ -342,7 +342,7 @@ describe Cask::DSL, :cask do
       let(:token) { "with-depends-on-formula" }
 
       it "allows depends_on formula to be specified" do
-        expect(cask.depends_on.formula).not_to be nil
+        expect(cask.depends_on.formula).not_to be_nil
       end
     end
 
@@ -350,7 +350,7 @@ describe Cask::DSL, :cask do
       let(:token) { "with-depends-on-formula-multiple" }
 
       it "allows multiple depends_on formula to be specified" do
-        expect(cask.depends_on.formula).not_to be nil
+        expect(cask.depends_on.formula).not_to be_nil
       end
     end
   end
@@ -360,7 +360,7 @@ describe Cask::DSL, :cask do
       let(:token) { "with-depends-on-cask" }
 
       it "is allowed" do
-        expect(cask.depends_on.cask).not_to be nil
+        expect(cask.depends_on.cask).not_to be_nil
       end
     end
 
@@ -368,7 +368,7 @@ describe Cask::DSL, :cask do
       let(:token) { "with-depends-on-cask-multiple" }
 
       it "is allowed" do
-        expect(cask.depends_on.cask).not_to be nil
+        expect(cask.depends_on.cask).not_to be_nil
       end
     end
   end
@@ -396,7 +396,7 @@ describe Cask::DSL, :cask do
       let(:token) { "with-depends-on-arch" }
 
       it "is allowed to be specified" do
-        expect(cask.depends_on.arch).not_to be nil
+        expect(cask.depends_on.arch).not_to be_nil
       end
     end
 
diff --git a/Library/Homebrew/test/cli/parser_spec.rb b/Library/Homebrew/test/cli/parser_spec.rb
index 69eea85296..54dc168d65 100644
--- a/Library/Homebrew/test/cli/parser_spec.rb
+++ b/Library/Homebrew/test/cli/parser_spec.rb
@@ -41,7 +41,7 @@ describe Homebrew::CLI::Parser do
 
       it "does not set the positive name if the positive flag is not passed" do
         args = parser.parse([])
-        expect(args.positive?).to be nil
+        expect(args.positive?).to be_nil
       end
     end
 
diff --git a/Library/Homebrew/test/commands_spec.rb b/Library/Homebrew/test/commands_spec.rb
index d817a4c80a..be8f748a6a 100644
--- a/Library/Homebrew/test/commands_spec.rb
+++ b/Library/Homebrew/test/commands_spec.rb
@@ -70,7 +70,7 @@ describe Commands do
     specify "returns the path for an internal command" do
       expect(described_class.path("rbcmd")).to eq(HOMEBREW_LIBRARY_PATH/"cmd/rbcmd.rb")
       expect(described_class.path("shcmd")).to eq(HOMEBREW_LIBRARY_PATH/"cmd/shcmd.sh")
-      expect(described_class.path("idontexist1234")).to be nil
+      expect(described_class.path("idontexist1234")).to be_nil
     end
 
     specify "returns the path for an internal developer-command" do
diff --git a/Library/Homebrew/test/dependency_collector_spec.rb b/Library/Homebrew/test/dependency_collector_spec.rb
index bff6a44f41..a12c3c6127 100644
--- a/Library/Homebrew/test/dependency_collector_spec.rb
+++ b/Library/Homebrew/test/dependency_collector_spec.rb
@@ -65,7 +65,7 @@ describe DependencyCollector do
     it "creates a resource dependency from a '.gz' URL" do
       resource = Resource.new
       resource.url("https://brew.sh/foo.tar.gz")
-      expect(collector.add(resource)).to be nil
+      expect(collector.add(resource)).to be_nil
     end
 
     it "creates a resource dependency from a '.lz' URL" do
diff --git a/Library/Homebrew/test/dev-cmd/audit_spec.rb b/Library/Homebrew/test/dev-cmd/audit_spec.rb
index d0f27dfe20..ecf0803ffd 100644
--- a/Library/Homebrew/test/dev-cmd/audit_spec.rb
+++ b/Library/Homebrew/test/dev-cmd/audit_spec.rb
@@ -46,7 +46,7 @@ module Homebrew
       expect(ft).to have_trailing_newline
 
       expect(ft =~ /\burl\b/).to be_truthy
-      expect(ft.line_number(/desc/)).to be nil
+      expect(ft.line_number(/desc/)).to be_nil
       expect(ft.line_number(/\burl\b/)).to eq(2)
       expect(ft).to include("Valid")
     end
diff --git a/Library/Homebrew/test/diagnostic_checks_spec.rb b/Library/Homebrew/test/diagnostic_checks_spec.rb
index 2863a9604c..17b34b0398 100644
--- a/Library/Homebrew/test/diagnostic_checks_spec.rb
+++ b/Library/Homebrew/test/diagnostic_checks_spec.rb
@@ -68,7 +68,7 @@ describe Homebrew::Diagnostic::Checks do
     ENV["PATH"] = ENV["PATH"].gsub \
       %r{(?:^|#{File::PATH_SEPARATOR})#{HOMEBREW_PREFIX}/bin}o, ""
 
-    expect(checks.check_user_path_1).to be nil
+    expect(checks.check_user_path_1).to be_nil
     expect(checks.check_user_path_2)
       .to match("Homebrew's \"bin\" was not found in your PATH.")
   end
@@ -80,8 +80,8 @@ describe Homebrew::Diagnostic::Checks do
       ENV["HOMEBREW_PATH"].gsub(/(?:^|#{Regexp.escape(File::PATH_SEPARATOR)})#{Regexp.escape(sbin)}/, "")
     (sbin/"something").mkpath
 
-    expect(checks.check_user_path_1).to be nil
-    expect(checks.check_user_path_2).to be nil
+    expect(checks.check_user_path_1).to be_nil
+    expect(checks.check_user_path_2).to be_nil
     expect(checks.check_user_path_3)
       .to match("Homebrew's \"sbin\" was not found in your PATH")
   ensure
diff --git a/Library/Homebrew/test/exceptions_spec.rb b/Library/Homebrew/test/exceptions_spec.rb
index dfa8e9b6bc..054efd2db1 100644
--- a/Library/Homebrew/test/exceptions_spec.rb
+++ b/Library/Homebrew/test/exceptions_spec.rb
@@ -47,12 +47,12 @@ describe "Exception" do
 
     describe "#dependent_s" do
       it "returns nil if there is no dependent" do
-        expect(error.dependent_s).to be nil
+        expect(error.dependent_s).to be_nil
       end
 
       it "returns nil if it depended on by itself" do
         error.dependent = "foo"
-        expect(error.dependent_s).to be nil
+        expect(error.dependent_s).to be_nil
       end
 
       it "returns a string if there is a dependent" do
diff --git a/Library/Homebrew/test/formula_spec.rb b/Library/Homebrew/test/formula_spec.rb
index 8f31f76d62..a705af58a8 100644
--- a/Library/Homebrew/test/formula_spec.rb
+++ b/Library/Homebrew/test/formula_spec.rb
@@ -38,9 +38,9 @@ describe Formula do
       expect(f.full_name).to eq(name)
       expect(f.full_specified_name).to eq(name)
       expect(f.path).to eq(path)
-      expect(f.alias_path).to be nil
-      expect(f.alias_name).to be nil
-      expect(f.full_alias_name).to be nil
+      expect(f.alias_path).to be_nil
+      expect(f.alias_name).to be_nil
+      expect(f.full_alias_name).to be_nil
       expect(f.specified_path).to eq(path)
       expect { klass.new }.to raise_error(ArgumentError)
     end
@@ -70,9 +70,9 @@ describe Formula do
         expect(f.full_name).to eq(full_name)
         expect(f.full_specified_name).to eq(full_name)
         expect(f.path).to eq(path)
-        expect(f.alias_path).to be nil
-        expect(f.alias_name).to be nil
-        expect(f.full_alias_name).to be nil
+        expect(f.alias_path).to be_nil
+        expect(f.alias_name).to be_nil
+        expect(f.full_alias_name).to be_nil
         expect(f.specified_path).to eq(path)
         expect { klass.new }.to raise_error(ArgumentError)
       end
@@ -175,9 +175,9 @@ describe Formula do
     ]
     build_values_with_no_installed_alias.each do |build|
       f.build = build
-      expect(f.installed_alias_path).to be nil
-      expect(f.installed_alias_name).to be nil
-      expect(f.full_installed_alias_name).to be nil
+      expect(f.installed_alias_path).to be_nil
+      expect(f.installed_alias_name).to be_nil
+      expect(f.full_installed_alias_name).to be_nil
       expect(f.installed_specified_name).to eq(f.name)
       expect(f.full_installed_specified_name).to eq(f.name)
     end
@@ -210,9 +210,9 @@ describe Formula do
     ]
     build_values_with_no_installed_alias.each do |build|
       f.build = build
-      expect(f.installed_alias_path).to be nil
-      expect(f.installed_alias_name).to be nil
-      expect(f.full_installed_alias_name).to be nil
+      expect(f.installed_alias_path).to be_nil
+      expect(f.installed_alias_name).to be_nil
+      expect(f.full_installed_alias_name).to be_nil
       expect(f.installed_specified_name).to eq(f.name)
       expect(f.full_installed_specified_name).to eq(f.full_name)
     end
@@ -401,7 +401,7 @@ describe Formula do
   end
 
   specify "#<=>" do
-    expect(Testball.new <=> Object.new).to be nil
+    expect(Testball.new <=> Object.new).to be_nil
   end
 
   describe "#installed_alias_path" do
@@ -414,7 +414,7 @@ describe Formula do
       f.build = BuildOptions.new(Options.new, f.options)
 
       expect(f.alias_path).to eq(alias_path)
-      expect(f.installed_alias_path).to be nil
+      expect(f.installed_alias_path).to be_nil
     end
 
     example "alias paths with tab with non alias source path" do
@@ -427,7 +427,7 @@ describe Formula do
       f.build = Tab.new(source: { "path" => source_path.to_s })
 
       expect(f.alias_path).to eq(alias_path)
-      expect(f.installed_alias_path).to be nil
+      expect(f.installed_alias_path).to be_nil
     end
 
     example "alias paths with tab with alias source path" do
@@ -580,7 +580,7 @@ describe Formula do
       url "foo-1.0"
     end
 
-    expect(f.head).to be nil
+    expect(f.head).to be_nil
   end
 
   it "honors attributes declared before specs" do
@@ -1132,7 +1132,7 @@ describe Formula do
     specify "alias changes when not installed with alias" do
       tab.source["path"] = Formulary.core_path(f.name).to_s
 
-      expect(f.current_installed_alias_target).to be nil
+      expect(f.current_installed_alias_target).to be_nil
       expect(f.latest_formula).to eq(f)
       expect(f).not_to have_changed_installed_alias_target
       expect(f).not_to supersede_an_installed_formula
@@ -1526,7 +1526,7 @@ describe Formula do
     end
 
     it "returns nil when not installed" do
-      expect(f.any_installed_version).to be nil
+      expect(f.any_installed_version).to be_nil
     end
 
     it "returns package version when installed" do
diff --git a/Library/Homebrew/test/formula_spec_selection_spec.rb b/Library/Homebrew/test/formula_spec_selection_spec.rb
index c16c13ad5c..587d0d1ff6 100644
--- a/Library/Homebrew/test/formula_spec_selection_spec.rb
+++ b/Library/Homebrew/test/formula_spec_selection_spec.rb
@@ -40,7 +40,7 @@ describe Formula do
         head "foo"
       end
 
-      expect(f.stable).to be nil
+      expect(f.stable).to be_nil
       expect(f).to be_head
     end
 
diff --git a/Library/Homebrew/test/installed_dependents_spec.rb b/Library/Homebrew/test/installed_dependents_spec.rb
index 824c6f2d94..3843cff6bb 100644
--- a/Library/Homebrew/test/installed_dependents_spec.rb
+++ b/Library/Homebrew/test/installed_dependents_spec.rb
@@ -81,7 +81,7 @@ describe InstalledDependents do
 
     specify "no dependencies anywhere" do
       dependencies nil
-      expect(described_class.find_some_installed_dependents([keg])).to be nil
+      expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "missing Formula dependency" do
@@ -93,7 +93,7 @@ describe InstalledDependents do
     specify "uninstalling dependent and dependency" do
       dependencies nil
       Formula["bar"].class.depends_on "foo"
-      expect(described_class.find_some_installed_dependents([keg, dependent])).to be nil
+      expect(described_class.find_some_installed_dependents([keg, dependent])).to be_nil
     end
 
     specify "renamed dependency" do
@@ -112,7 +112,7 @@ describe InstalledDependents do
 
     specify "empty dependencies in Tab" do
       dependencies []
-      expect(described_class.find_some_installed_dependents([keg])).to be nil
+      expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "same name but different version in Tab" do
@@ -123,7 +123,7 @@ describe InstalledDependents do
     specify "different name and same version in Tab" do
       stub_formula_name("baz")
       dependencies [{ "full_name" => "baz", "version" => keg.version.to_s }]
-      expect(described_class.find_some_installed_dependents([keg])).to be nil
+      expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "same name and version in Tab" do
@@ -140,7 +140,7 @@ describe InstalledDependents do
     specify "non-opt-linked" do
       keg.remove_opt_record
       dependencies [{ "full_name" => "foo", "version" => "1.0" }]
-      expect(described_class.find_some_installed_dependents([keg])).to be nil
+      expect(described_class.find_some_installed_dependents([keg])).to be_nil
     end
 
     specify "keg-only" do
diff --git a/Library/Homebrew/test/keg_spec.rb b/Library/Homebrew/test/keg_spec.rb
index 1b82ada38b..cbc99ef0b7 100644
--- a/Library/Homebrew/test/keg_spec.rb
+++ b/Library/Homebrew/test/keg_spec.rb
@@ -55,7 +55,7 @@ describe Keg do
   end
 
   specify "#oldname_opt_record" do
-    expect(keg.oldname_opt_record).to be nil
+    expect(keg.oldname_opt_record).to be_nil
     oldname_opt_record = HOMEBREW_PREFIX/"opt/oldfoo"
     oldname_opt_record.make_relative_symlink(HOMEBREW_CELLAR/"foo/1.0")
     expect(keg.oldname_opt_record).to eq(oldname_opt_record)
diff --git a/Library/Homebrew/test/livecheck/strategy/sparkle_spec.rb b/Library/Homebrew/test/livecheck/strategy/sparkle_spec.rb
index 63540ef2f1..87f94bb6ea 100644
--- a/Library/Homebrew/test/livecheck/strategy/sparkle_spec.rb
+++ b/Library/Homebrew/test/livecheck/strategy/sparkle_spec.rb
@@ -68,7 +68,7 @@ describe Homebrew::Livecheck::Strategy::Sparkle do
     let(:item_from_appcast_xml) { sparkle.item_from_content(appcast_xml) }
 
     it "returns nil if content is blank" do
-      expect(sparkle.item_from_content("")).to be nil
+      expect(sparkle.item_from_content("")).to be_nil
     end
 
     it "returns an Item when given XML data" do
diff --git a/Library/Homebrew/test/livecheck_spec.rb b/Library/Homebrew/test/livecheck_spec.rb
index 7e4b0db27b..aa5afde716 100644
--- a/Library/Homebrew/test/livecheck_spec.rb
+++ b/Library/Homebrew/test/livecheck_spec.rb
@@ -30,7 +30,7 @@ describe Livecheck do
 
   describe "#formula" do
     it "returns nil if not set" do
-      expect(livecheckable_f.formula).to be nil
+      expect(livecheckable_f.formula).to be_nil
     end
 
     it "returns the String if set" do
@@ -47,7 +47,7 @@ describe Livecheck do
 
   describe "#cask" do
     it "returns nil if not set" do
-      expect(livecheckable_c.cask).to be nil
+      expect(livecheckable_c.cask).to be_nil
     end
 
     it "returns the String if set" do
@@ -64,7 +64,7 @@ describe Livecheck do
 
   describe "#regex" do
     it "returns nil if not set" do
-      expect(livecheckable_f.regex).to be nil
+      expect(livecheckable_f.regex).to be_nil
     end
 
     it "returns the Regexp if set" do
@@ -83,7 +83,7 @@ describe Livecheck do
     it "sets @skip to true when no argument is provided" do
       expect(livecheckable_f.skip).to be true
       expect(livecheckable_f.instance_variable_get(:@skip)).to be true
-      expect(livecheckable_f.instance_variable_get(:@skip_msg)).to be nil
+      expect(livecheckable_f.instance_variable_get(:@skip_msg)).to be_nil
     end
 
     it "sets @skip to true and @skip_msg to the provided String" do
@@ -110,7 +110,7 @@ describe Livecheck do
 
   describe "#strategy" do
     it "returns nil if not set" do
-      expect(livecheckable_f.strategy).to be nil
+      expect(livecheckable_f.strategy).to be_nil
     end
 
     it "returns the Symbol if set" do
@@ -129,7 +129,7 @@ describe Livecheck do
     let(:url_string) { "https://brew.sh" }
 
     it "returns nil if not set" do
-      expect(livecheckable_f.url).to be nil
+      expect(livecheckable_f.url).to be_nil
     end
 
     it "returns a string when set to a string" do
diff --git a/Library/Homebrew/test/os/linux/dependency_collector_spec.rb b/Library/Homebrew/test/os/linux/dependency_collector_spec.rb
index 02a6362dc7..8943f93ac4 100644
--- a/Library/Homebrew/test/os/linux/dependency_collector_spec.rb
+++ b/Library/Homebrew/test/os/linux/dependency_collector_spec.rb
@@ -35,19 +35,19 @@ describe DependencyCollector do
       it "does not create a resource dependency from a '.xz' URL" do
         resource.url("https://brew.sh/foo.xz")
         allow_any_instance_of(Object).to receive(:which).with("xz").and_return(Pathname.new("foo"))
-        expect(collector.add(resource)).to be nil
+        expect(collector.add(resource)).to be_nil
       end
 
       it "does not create a resource dependency from a '.zip' URL" do
         resource.url("https://brew.sh/foo.zip")
         allow_any_instance_of(Object).to receive(:which).with("unzip").and_return(Pathname.new("foo"))
-        expect(collector.add(resource)).to be nil
+        expect(collector.add(resource)).to be_nil
       end
 
       it "does not create a resource dependency from a '.bz2' URL" do
         resource.url("https://brew.sh/foo.tar.bz2")
         allow_any_instance_of(Object).to receive(:which).with("bzip2").and_return(Pathname.new("foo"))
-        expect(collector.add(resource)).to be nil
+        expect(collector.add(resource)).to be_nil
       end
     end
   end
diff --git a/Library/Homebrew/test/os/mac/dependency_collector_spec.rb b/Library/Homebrew/test/os/mac/dependency_collector_spec.rb
index cad682f1a1..9d6948de4c 100644
--- a/Library/Homebrew/test/os/mac/dependency_collector_spec.rb
+++ b/Library/Homebrew/test/os/mac/dependency_collector_spec.rb
@@ -11,34 +11,34 @@ describe DependencyCollector do
   specify "Resource dependency from a '.xz' URL" do
     resource = Resource.new
     resource.url("https://brew.sh/foo.tar.xz")
-    expect(collector.add(resource)).to be nil
+    expect(collector.add(resource)).to be_nil
   end
 
   specify "Resource dependency from a '.zip' URL" do
     resource = Resource.new
     resource.url("https://brew.sh/foo.zip")
-    expect(collector.add(resource)).to be nil
+    expect(collector.add(resource)).to be_nil
   end
 
   specify "Resource dependency from a '.bz2' URL" do
     resource = Resource.new
     resource.url("https://brew.sh/foo.tar.bz2")
-    expect(collector.add(resource)).to be nil
+    expect(collector.add(resource)).to be_nil
   end
 
   specify "Resource dependency from a '.git' URL" do
     resource = Resource.new
     resource.url("git://brew.sh/foo/bar.git")
-    expect(collector.add(resource)).to be nil
+    expect(collector.add(resource)).to be_nil
   end
 
   specify "Resource dependency from a Subversion URL" do
     resource = Resource.new
     resource.url("svn://brew.sh/foo/bar")
     if MacOS.version < :catalina
-      expect(collector.add(resource)).to be nil
+      expect(collector.add(resource)).to be_nil
     else
-      expect(collector.add(resource)).not_to be nil
+      expect(collector.add(resource)).not_to be_nil
     end
   end
 end
diff --git a/Library/Homebrew/test/pkg_version_spec.rb b/Library/Homebrew/test/pkg_version_spec.rb
index 2ff51a01f4..517580c800 100644
--- a/Library/Homebrew/test/pkg_version_spec.rb
+++ b/Library/Homebrew/test/pkg_version_spec.rb
@@ -56,12 +56,12 @@ describe PkgVersion do
 
   describe "#<=>" do
     it "returns nil if the comparison fails" do
-      expect(described_class.new(Version.create("1.0"), 0) <=> Object.new).to be nil
-      expect(Object.new <=> described_class.new(Version.create("1.0"), 0)).to be nil
-      expect(Object.new <=> described_class.new(Version.create("1.0"), 0)).to be nil
-      expect(described_class.new(Version.create("1.0"), 0) <=> nil).to be nil
+      expect(described_class.new(Version.create("1.0"), 0) <=> Object.new).to be_nil
+      expect(Object.new <=> described_class.new(Version.create("1.0"), 0)).to be_nil
+      expect(Object.new <=> described_class.new(Version.create("1.0"), 0)).to be_nil
+      expect(described_class.new(Version.create("1.0"), 0) <=> nil).to be_nil
       # This one used to fail due to dereferencing a null `self`
-      expect(described_class.new(nil, 0) <=> described_class.new(Version.create("1.0"), 0)).to be nil
+      expect(described_class.new(nil, 0) <=> described_class.new(Version.create("1.0"), 0)).to be_nil
     end
   end
 
diff --git a/Library/Homebrew/test/requirement_spec.rb b/Library/Homebrew/test/requirement_spec.rb
index 4fe5cad5a1..0cd1c0db19 100644
--- a/Library/Homebrew/test/requirement_spec.rb
+++ b/Library/Homebrew/test/requirement_spec.rb
@@ -180,7 +180,7 @@ describe Requirement do
       let(:klass) { Class.new(described_class) }
 
       it "returns nil" do
-        expect(requirement.modify_build_environment).to be nil
+        expect(requirement.modify_build_environment).to be_nil
       end
     end
   end
diff --git a/Library/Homebrew/test/resource_spec.rb b/Library/Homebrew/test/resource_spec.rb
index 29513698e0..63a14b0b1e 100644
--- a/Library/Homebrew/test/resource_spec.rb
+++ b/Library/Homebrew/test/resource_spec.rb
@@ -85,7 +85,7 @@ describe Resource do
     end
 
     it "returns nil if unset" do
-      expect(resource.version).to be nil
+      expect(resource.version).to be_nil
     end
   end
 
@@ -103,7 +103,7 @@ describe Resource do
 
   describe "#checksum" do
     it "returns nil if unset" do
-      expect(resource.checksum).to be nil
+      expect(resource.checksum).to be_nil
     end
 
     it "returns the checksum set with #sha256" do
diff --git a/Library/Homebrew/test/software_spec/head_spec.rb b/Library/Homebrew/test/software_spec/head_spec.rb
index 89ee2ca6b9..0f92ba4be6 100644
--- a/Library/Homebrew/test/software_spec/head_spec.rb
+++ b/Library/Homebrew/test/software_spec/head_spec.rb
@@ -11,6 +11,6 @@ describe HeadSoftwareSpec do
   end
 
   specify "#verify_download_integrity" do
-    expect(head_spec.verify_download_integrity(Object.new)).to be nil
+    expect(head_spec.verify_download_integrity(Object.new)).to be_nil
   end
 end
diff --git a/Library/Homebrew/test/system_command_result_spec.rb b/Library/Homebrew/test/system_command_result_spec.rb
index a4995c8b13..fd82a100bf 100644
--- a/Library/Homebrew/test/system_command_result_spec.rb
+++ b/Library/Homebrew/test/system_command_result_spec.rb
@@ -170,7 +170,7 @@ describe SystemCommand::Result do
       let(:stdout) { "" }
 
       it "returns nil" do
-        expect(result_plist).to be nil
+        expect(result_plist).to be_nil
       end
     end
   end
diff --git a/Library/Homebrew/test/tab_spec.rb b/Library/Homebrew/test/tab_spec.rb
index 24b64daf5a..85b6ec12d0 100644
--- a/Library/Homebrew/test/tab_spec.rb
+++ b/Library/Homebrew/test/tab_spec.rb
@@ -64,20 +64,20 @@ describe Tab do
     expect(tab.homebrew_version).to eq(HOMEBREW_VERSION)
     expect(tab.unused_options).to be_empty
     expect(tab.used_options).to be_empty
-    expect(tab.changed_files).to be nil
+    expect(tab.changed_files).to be_nil
     expect(tab).not_to be_built_as_bottle
     expect(tab).not_to be_poured_from_bottle
     expect(tab).to be_stable
     expect(tab).not_to be_head
-    expect(tab.tap).to be nil
-    expect(tab.time).to be nil
-    expect(tab.HEAD).to be nil
-    expect(tab.runtime_dependencies).to be nil
-    expect(tab.stable_version).to be nil
-    expect(tab.head_version).to be nil
+    expect(tab.tap).to be_nil
+    expect(tab.time).to be_nil
+    expect(tab.HEAD).to be_nil
+    expect(tab.runtime_dependencies).to be_nil
+    expect(tab.stable_version).to be_nil
+    expect(tab.head_version).to be_nil
     expect(tab.cxxstdlib.compiler).to eq(DevelopmentTools.default_compiler)
-    expect(tab.cxxstdlib.type).to be nil
-    expect(tab.source["path"]).to be nil
+    expect(tab.cxxstdlib.type).to be_nil
+    expect(tab.source["path"]).to be_nil
   end
 
   specify "#include?" do
@@ -114,25 +114,25 @@ describe Tab do
 
   specify "#runtime_dependencies" do
     tab = described_class.new
-    expect(tab.runtime_dependencies).to be nil
+    expect(tab.runtime_dependencies).to be_nil
 
     tab.homebrew_version = "1.1.6"
-    expect(tab.runtime_dependencies).to be nil
+    expect(tab.runtime_dependencies).to be_nil
 
     tab.runtime_dependencies = []
-    expect(tab.runtime_dependencies).not_to be nil
+    expect(tab.runtime_dependencies).not_to be_nil
 
     tab.homebrew_version = "1.1.5"
-    expect(tab.runtime_dependencies).to be nil
+    expect(tab.runtime_dependencies).to be_nil
 
     tab.homebrew_version = "1.1.7"
-    expect(tab.runtime_dependencies).not_to be nil
+    expect(tab.runtime_dependencies).not_to be_nil
 
     tab.homebrew_version = "1.1.10"
-    expect(tab.runtime_dependencies).not_to be nil
+    expect(tab.runtime_dependencies).not_to be_nil
 
     tab.runtime_dependencies = [{ "full_name" => "foo", "version" => "1.0" }]
-    expect(tab.runtime_dependencies).not_to be nil
+    expect(tab.runtime_dependencies).not_to be_nil
   end
 
   specify "::runtime_deps_hash" do
@@ -232,7 +232,7 @@ describe Tab do
       expect(tab.HEAD).to eq(TEST_SHA1)
       expect(tab.cxxstdlib.compiler).to eq(:clang)
       expect(tab.cxxstdlib.type).to eq(:libcxx)
-      expect(tab.runtime_dependencies).to be nil
+      expect(tab.runtime_dependencies).to be_nil
     end
 
     it "raises a parse exception message including the Tab filename" do
@@ -331,7 +331,7 @@ describe Tab do
       f.prefix.mkpath
 
       tab = described_class.for_formula(f)
-      expect(tab.tabfile).to be nil
+      expect(tab.tabfile).to be_nil
     end
 
     it "can create a Tab for a Formula with multiple Kegs" do
diff --git a/Library/Homebrew/test/tap_spec.rb b/Library/Homebrew/test/tap_spec.rb
index ae7ef7a253..bde5abb829 100644
--- a/Library/Homebrew/test/tap_spec.rb
+++ b/Library/Homebrew/test/tap_spec.rb
@@ -156,7 +156,7 @@ describe Tap do
     expect(homebrew_foo_tap.issues_url).to eq("https://github.com/Homebrew/homebrew-foo/issues")
 
     (Tap::TAP_DIRECTORY/"someone/homebrew-no-git").mkpath
-    expect(described_class.new("someone", "no-git").issues_url).to be nil
+    expect(described_class.new("someone", "no-git").issues_url).to be_nil
   ensure
     path.parent.rmtree
   end
@@ -198,13 +198,13 @@ describe Tap do
     end
 
     it "returns nil if the Tap is not a Git repository" do
-      expect(homebrew_foo_tap.remote).to be nil
+      expect(homebrew_foo_tap.remote).to be_nil
     end
 
     it "returns nil if Git is not available" do
       setup_git_repo
       allow(Utils::Git).to receive(:available?).and_return(false)
-      expect(homebrew_foo_tap.remote).to be nil
+      expect(homebrew_foo_tap.remote).to be_nil
     end
   end
 
@@ -240,13 +240,13 @@ describe Tap do
     end
 
     it "returns nil if the Tap is not a Git repository" do
-      expect(homebrew_foo_tap.remote_repo).to be nil
+      expect(homebrew_foo_tap.remote_repo).to be_nil
     end
 
     it "returns nil if Git is not available" do
       setup_git_repo
       allow(Utils::Git).to receive(:available?).and_return(false)
-      expect(homebrew_foo_tap.remote_repo).to be nil
+      expect(homebrew_foo_tap.remote_repo).to be_nil
     end
   end
 
@@ -450,11 +450,11 @@ describe Tap do
   specify "#config" do
     setup_git_repo
 
-    expect(homebrew_foo_tap.config["foo"]).to be nil
+    expect(homebrew_foo_tap.config["foo"]).to be_nil
     homebrew_foo_tap.config["foo"] = "bar"
     expect(homebrew_foo_tap.config["foo"]).to eq("bar")
     homebrew_foo_tap.config["foo"] = nil
-    expect(homebrew_foo_tap.config["foo"]).to be nil
+    expect(homebrew_foo_tap.config["foo"]).to be_nil
   end
 
   describe "#each" do
diff --git a/Library/Homebrew/test/utils/bottles/collector_spec.rb b/Library/Homebrew/test/utils/bottles/collector_spec.rb
index 696cabc76f..79a571fc4b 100644
--- a/Library/Homebrew/test/utils/bottles/collector_spec.rb
+++ b/Library/Homebrew/test/utils/bottles/collector_spec.rb
@@ -21,12 +21,12 @@ describe Utils::Bottles::Collector do
     end
 
     it "returns nil if empty" do
-      expect(collector.specification_for(Utils::Bottles::Tag.from_symbol(:foo))).to be nil
+      expect(collector.specification_for(Utils::Bottles::Tag.from_symbol(:foo))).to be_nil
     end
 
     it "returns nil when there is no match" do
       collector.add(catalina, checksum: Checksum.new("bar_checksum"), cellar: "bar_cellar")
-      expect(collector.specification_for(Utils::Bottles::Tag.from_symbol(:foo))).to be nil
+      expect(collector.specification_for(Utils::Bottles::Tag.from_symbol(:foo))).to be_nil
     end
 
     it "uses older tags when needed", :needs_macos do
diff --git a/Library/Homebrew/test/utils/shell_spec.rb b/Library/Homebrew/test/utils/shell_spec.rb
index 02f795bee3..d83372f85c 100644
--- a/Library/Homebrew/test/utils/shell_spec.rb
+++ b/Library/Homebrew/test/utils/shell_spec.rb
@@ -56,9 +56,9 @@ describe Utils::Shell do
     end
 
     it "returns nil when input is invalid" do
-      expect(described_class.from_path("")).to be nil
-      expect(described_class.from_path("@@@@@@")).to be nil
-      expect(described_class.from_path("invalid_shell-4.2")).to be nil
+      expect(described_class.from_path("")).to be_nil
+      expect(described_class.from_path("@@@@@@")).to be_nil
+      expect(described_class.from_path("invalid_shell-4.2")).to be_nil
     end
   end
 
diff --git a/Library/Homebrew/test/utils_spec.rb b/Library/Homebrew/test/utils_spec.rb
index f92d0bbcde..a729d9988d 100644
--- a/Library/Homebrew/test/utils_spec.rb
+++ b/Library/Homebrew/test/utils_spec.rb
@@ -132,7 +132,7 @@ describe "globally-scoped helper methods" do
     end
 
     it "skips non-executables" do
-      expect(which(File.basename(cmd), File.dirname(cmd))).to be nil
+      expect(which(File.basename(cmd), File.dirname(cmd))).to be_nil
     end
 
     it "skips malformed path and doesn't fail" do
diff --git a/Library/Homebrew/test/version_spec.rb b/Library/Homebrew/test/version_spec.rb
index c387836786..c7bff88004 100644
--- a/Library/Homebrew/test/version_spec.rb
+++ b/Library/Homebrew/test/version_spec.rb
@@ -35,13 +35,13 @@ describe Version do
 
     specify "comparison returns nil for non-token" do
       v = described_class.create("1")
-      expect(v <=> Object.new).to be nil
+      expect(v <=> Object.new).to be_nil
       expect { v > Object.new }.to raise_error(ArgumentError)
     end
 
     describe "#to_str" do
       it "implicitly converts token to string" do
-        expect(String.try_convert(described_class.new("foo"))).not_to be nil
+        expect(String.try_convert(described_class.new("foo"))).not_to be_nil
       end
     end
   end
@@ -211,7 +211,7 @@ describe Version do
 
   specify "comparison returns nil for non-version" do
     v = described_class.create("1.0")
-    expect(v <=> Object.new).to be nil
+    expect(v <=> Object.new).to be_nil
     expect { v > Object.new }.to raise_error(ArgumentError)
   end
 
@@ -271,7 +271,7 @@ describe Version do
 
     specify "HEAD without commit" do
       v = described_class.create("HEAD")
-      expect(v.commit).to be nil
+      expect(v.commit).to be_nil
       expect(v.to_str).to eq("HEAD")
     end
   end
@@ -326,7 +326,7 @@ describe Version do
 
   describe "#minor" do
     it "returns minor version token" do
-      expect(described_class.create("1").minor).to be nil
+      expect(described_class.create("1").minor).to be_nil
       expect(described_class.create("1.2").minor).to be == Version::Token.create("2")
       expect(described_class.create("1.2.3").minor).to be == Version::Token.create("2")
       expect(described_class.create("1.2.3alpha").minor).to be == Version::Token.create("2")
@@ -340,8 +340,8 @@ describe Version do
 
   describe "#patch" do
     it "returns patch version token" do
-      expect(described_class.create("1").patch).to be nil
-      expect(described_class.create("1.2").patch).to be nil
+      expect(described_class.create("1").patch).to be_nil
+      expect(described_class.create("1.2").patch).to be_nil
       expect(described_class.create("1.2.3").patch).to be == Version::Token.create("3")
       expect(described_class.create("1.2.3alpha").patch).to be == Version::Token.create("3")
       expect(described_class.create("1.2.3alpha4").patch).to be == Version::Token.create("3")