diff --git a/Library/Homebrew/test/os/mac/pkgconfig_spec.rb b/Library/Homebrew/test/os/mac/pkgconfig_spec.rb
new file mode 100644
index 0000000000000..fa8a1de35b5f1
--- /dev/null
+++ b/Library/Homebrew/test/os/mac/pkgconfig_spec.rb
@@ -0,0 +1,126 @@
+# frozen_string_literal: true
+
+# These tests assume the needed SDKs are correctly installed, i.e. `brew doctor` passes.
+# The CLT version installed should be the latest available for the running OS.
+# The tests do not check other OS versions beyond than the one the tests are being run on.
+#
+# It is not possible to automatically check the following libraries for version updates:
+#
+# - libedit (incorrect LIBEDIT_MAJOR/MINOR in histedit.h)
+# - uuid (not a standalone library)
+#
+# Additionally, libffi version detection cannot be performed on systems running Mojave or earlier.
+#
+# For indeterminable cases, consult https://opensource.apple.com for the version used.
+describe "pkg-config" do
+  def pc_version(library)
+    path = HOMEBREW_LIBRARY_PATH/"os/mac/pkgconfig/#{MacOS.version}/#{library}.pc"
+    version = File.foreach(path)
+                  .lazy
+                  .grep(/^Version:\s*?(.+)$/) { Regexp.last_match(1) }
+                  .first
+                  .strip
+    if (match = version.match(/^\${(.+?)}$/))
+      version = File.foreach(path)
+                    .lazy
+                    .grep(/^#{match.captures.first}\s*?=\s*?(.+)$/) { Regexp.last_match(1) }
+                    .first
+                    .strip
+    end
+    version
+  end
+
+  let(:sdk) { MacOS.sdk_path_if_needed }
+
+  it "returns the correct version for expat" do
+    version = File.foreach("#{sdk}/usr/include/expat.h")
+                  .lazy
+                  .grep(/^#define XML_(MAJOR|MINOR|MICRO)_VERSION (\d+)$/) do
+                    { Regexp.last_match(1).downcase => Regexp.last_match(2) }
+                  end
+                  .inject(:merge!)
+    version = "#{version["major"]}.#{version["minor"]}.#{version["micro"]}"
+
+    expect(pc_version("expat")).to eq(version)
+  end
+
+  it "returns the correct version for libcurl" do
+    version = File.foreach("#{sdk}/usr/include/curl/curlver.h")
+                  .lazy
+                  .grep(/^#define LIBCURL_VERSION "(.*?)"$/) { Regexp.last_match(1) }
+                  .first
+
+    expect(pc_version("libcurl")).to eq(version)
+  end
+
+  it "returns the correct version for libexslt" do
+    version = File.foreach("#{sdk}/usr/include/libexslt/exsltconfig.h")
+                  .lazy
+                  .grep(/^#define LIBEXSLT_VERSION (\d+)$/) { Regexp.last_match(1) }
+                  .first
+                  .rjust(6, "0")
+    version = "#{version[-6..-5].to_i}.#{version[-4..-3].to_i}.#{version[-2..].to_i}"
+
+    expect(pc_version("libexslt")).to eq(version)
+  end
+
+  it "returns the correct version for libffi" do
+    version = File.foreach("#{sdk}/usr/include/ffi/ffi.h")
+                  .lazy
+                  .grep(/^\s*libffi (\S+) - Copyright /) { Regexp.last_match(1) }
+                  .first
+
+    skip "Cannot detect system libffi version." if version == "PyOBJC"
+
+    expect(pc_version("libffi")).to eq(version)
+  end
+
+  it "returns the correct version for libxml-2.0" do
+    version = File.foreach("#{sdk}/usr/include/libxml2/libxml/xmlversion.h")
+                  .lazy
+                  .grep(/^#define LIBXML_DOTTED_VERSION "(.*?)"$/) { Regexp.last_match(1) }
+                  .first
+
+    expect(pc_version("libxml-2.0")).to eq(version)
+  end
+
+  it "returns the correct version for libxslt" do
+    version = File.foreach("#{sdk}/usr/include/libxslt/xsltconfig.h")
+                  .lazy
+                  .grep(/^#define LIBXSLT_DOTTED_VERSION "(.*?)"$/) { Regexp.last_match(1) }
+                  .first
+
+    expect(pc_version("libxslt")).to eq(version)
+  end
+
+  it "returns the correct version for ncurses" do
+    version = File.foreach("#{sdk}/usr/include/ncurses.h")
+                  .lazy
+                  .grep(/^#define NCURSES_VERSION_(MAJOR|MINOR|PATCH) (\d+)$/) do
+                    { Regexp.last_match(1).downcase => Regexp.last_match(2) }
+                  end
+                  .inject(:merge!)
+    version = "#{version["major"]}.#{version["minor"]}.#{version["patch"]}"
+
+    expect(pc_version("ncurses")).to eq(version)
+    expect(pc_version("ncursesw")).to eq(version)
+  end
+
+  it "returns the correct version for sqlite3" do
+    version = File.foreach("#{sdk}/usr/include/sqlite3.h")
+                  .lazy
+                  .grep(/^#define SQLITE_VERSION\s+?"(.*?)"$/) { Regexp.last_match(1) }
+                  .first
+
+    expect(pc_version("sqlite3")).to eq(version)
+  end
+
+  it "returns the correct version for zlib" do
+    version = File.foreach("#{sdk}/usr/include/zlib.h")
+                  .lazy
+                  .grep(/^#define ZLIB_VERSION "(.*?)"$/) { Regexp.last_match(1) }
+                  .first
+
+    expect(pc_version("zlib")).to eq(version)
+  end
+end