diff --git a/Library/Homebrew/dev-cmd/man.rb b/Library/Homebrew/dev-cmd/man.rb
index 8d55043393..147a34ef9a 100644
--- a/Library/Homebrew/dev-cmd/man.rb
+++ b/Library/Homebrew/dev-cmd/man.rb
@@ -125,7 +125,7 @@ module Homebrew
       ronn.write markup
       ronn.close_write
       ronn_output = ronn.read
-      odie "Got no output from ronn!" unless ronn_output
+      odie "Got no output from ronn!" if ronn_output.blank?
       if format_flag == "--markdown"
         ronn_output = ronn_output.gsub(%r{<var>(.*?)</var>}, "*`\\1`*")
                                  .gsub(/\n\n\n+/, "\n\n")
diff --git a/Library/Homebrew/extend/os/mac/diagnostic.rb b/Library/Homebrew/extend/os/mac/diagnostic.rb
index 5d5e2eec9b..3116255fa2 100644
--- a/Library/Homebrew/extend/os/mac/diagnostic.rb
+++ b/Library/Homebrew/extend/os/mac/diagnostic.rb
@@ -139,7 +139,11 @@ module Homebrew
       end
 
       def check_ruby_version
-        ruby_version = "2.3.7"
+        ruby_version = if MacOS.version >= :catalina
+          "2.6.3"
+        else
+          "2.3.7"
+        end
         return if RUBY_VERSION == ruby_version
         return if ARGV.homebrew_developer? && OS::Mac.prerelease?
 
diff --git a/Library/Homebrew/system_command.rb b/Library/Homebrew/system_command.rb
index ec99b832bd..e524359a10 100644
--- a/Library/Homebrew/system_command.rb
+++ b/Library/Homebrew/system_command.rb
@@ -96,7 +96,7 @@ class SystemCommand
 
     return [] if set_variables.empty?
 
-    ["env", *set_variables]
+    ["/usr/bin/env", *set_variables]
   end
 
   def sudo_prefix
diff --git a/Library/Homebrew/test/support/fixtures/bottles/testball_bottle-0.1.catalina.bottle.tar.gz b/Library/Homebrew/test/support/fixtures/bottles/testball_bottle-0.1.catalina.bottle.tar.gz
new file mode 120000
index 0000000000..3e989830ba
--- /dev/null
+++ b/Library/Homebrew/test/support/fixtures/bottles/testball_bottle-0.1.catalina.bottle.tar.gz
@@ -0,0 +1 @@
+testball_bottle-0.1.yosemite.bottle.tar.gz
\ No newline at end of file
diff --git a/Library/Homebrew/test/support/helper/spec/shared_context/integration_test.rb b/Library/Homebrew/test/support/helper/spec/shared_context/integration_test.rb
index 6ce53e97f4..b61a0b0c14 100644
--- a/Library/Homebrew/test/support/helper/spec/shared_context/integration_test.rb
+++ b/Library/Homebrew/test/support/helper/spec/shared_context/integration_test.rb
@@ -47,8 +47,7 @@ RSpec.shared_context "integration test" do
 
       example.run
     ensure
-      FileUtils.rm HOMEBREW_PREFIX/"bin/brew"
-      FileUtils.rmdir HOMEBREW_PREFIX/"bin"
+      FileUtils.rm_r HOMEBREW_PREFIX/"bin"
     end
   end
 
diff --git a/Library/Homebrew/test/system_command_spec.rb b/Library/Homebrew/test/system_command_spec.rb
index 63675661a8..a10b4f485a 100644
--- a/Library/Homebrew/test/system_command_spec.rb
+++ b/Library/Homebrew/test/system_command_spec.rb
@@ -23,7 +23,7 @@ describe SystemCommand do
         it "includes the given variables explicitly" do
           expect(Open3)
             .to receive(:popen3)
-            .with(an_instance_of(Hash), ["env", "env"], "A=1", "B=2", "C=3", "env", *env_args, {})
+            .with(an_instance_of(Hash), ["/usr/bin/env", "/usr/bin/env"], "A=1", "B=2", "C=3", "env", *env_args, {})
             .and_call_original
 
           command.run!
@@ -49,7 +49,7 @@ describe SystemCommand do
           expect(Open3)
             .to receive(:popen3)
             .with(an_instance_of(Hash), ["/usr/bin/sudo", "/usr/bin/sudo"], "-E", "--",
-                  "env", "A=1", "B=2", "C=3", "env", *env_args, {})
+                  "/usr/bin/env", "A=1", "B=2", "C=3", "env", *env_args, {})
             .and_wrap_original do |original_popen3, *_, &block|
               original_popen3.call("true", &block)
             end
diff --git a/Library/Homebrew/test/unpack_strategy/subversion_spec.rb b/Library/Homebrew/test/unpack_strategy/subversion_spec.rb
index dc818221b4..74c4c80ad4 100644
--- a/Library/Homebrew/test/unpack_strategy/subversion_spec.rb
+++ b/Library/Homebrew/test/unpack_strategy/subversion_spec.rb
@@ -8,9 +8,8 @@ describe UnpackStrategy::Subversion, :needs_svn do
   let(:path) { working_copy }
 
   before do
-    system "svnadmin", "create", repo
-
-    system "svn", "checkout", "file://#{repo}", working_copy
+    safe_system "xcrun", "svnadmin", "create", repo
+    safe_system "svn", "checkout", "file://#{repo}", working_copy
 
     FileUtils.touch working_copy/"test"
     system "svn", "add", working_copy/"test"