Stop skipping ImageMagick tests in CI

activestorage-hotcell-client/test/test_helper.rb

@@ -21,6 +21,9 @@ class TemporarilyUnavailable < StandardError; end
 
   FIXTURES = File.expand_path("../../activestorage-hotcell-server/test/fixtures", __dir__)
 
+  # ImageMagick 7 runs `magick identify`; ImageMagick 6 has `identify` and no `magick`.
+  IDENTIFY = system("magick", "-version", out: File::NULL, err: File::NULL) ? %w[ magick identify ] : %w[ identify ]
+
   def setup
     HotCell.reset_registrations!
     HotCell.logger = Logger.new(File::NULL)
@@ -96,7 +99,7 @@ def with_active_storage_setting(name, value)
     end
 
     def identify(path)
-      lines = `magick identify -format '%w %h %m\n' #{path.shellescape} 2>/dev/null`.lines
+      lines = `#{IDENTIFY.shelljoin} -format '%w %h %m\n' #{path.shellescape} 2>/dev/null`.lines
       skip "ImageMagick is not installed" if lines.empty?
 
       width, height, format = lines.first.split

activestorage-hotcell-server/test/magick_environment_test.rb

@@ -34,8 +34,10 @@ def test_magick_does_not_inherit_the_workers_environment
   # The premise. Handed the same variable, `magick` in this process does refuse the fixture — so the
   # assertion above cannot pass because the policy was ineffective.
   def test_the_policy_does_refuse_a_magick_that_reads_it
+    skip "ImageMagick is not installed" unless magick_installed?
+
     with_refusing_policy_in_the_environment do |directory|
-      refused = system({ "MAGICK_CONFIGURE_PATH" => directory }, "magick", "identify", fixture("colour.png"),
+      refused = system({ "MAGICK_CONFIGURE_PATH" => directory }, *IDENTIFY, fixture("colour.png"),
                        out: File::NULL, err: File::NULL)
 
       refute refused, "the policy did not refuse PNG, so this test proves nothing"
@@ -176,14 +178,12 @@ def in_a_child(environment, script)
     # Both sides start from no bound at all: a runner holding one of its own would otherwise compare a
     # bounded pool against a bounded pool.
     def magick_installed?
-      system "magick", "-version", out: File::NULL, err: File::NULL
-    rescue Errno::ENOENT
-      false
+      system(*IDENTIFY, "-version", out: File::NULL, err: File::NULL)
     end
 
     def magick_thread_resource(environment)
       environment = { "OMP_NUM_THREADS" => nil, "OMP_THREAD_LIMIT" => nil }.merge(environment)
-      output = IO.popen([ environment, "magick", "-list", "resource" ], &:read)
+      output = IO.popen([ environment, *IDENTIFY, "-list", "resource" ], &:read)
 
       Integer(output[/Thread: (\d+)/, 1])
     rescue Errno::ENOENT

activestorage-hotcell-server/test/previewers_test.rb

@@ -269,7 +269,7 @@ def test_a_preview_reports_no_dimensions_because_rails_previewers_do_not_either
     # Mean intensity over the whole image, 0 black to 1 white, from ImageMagick so the claim does not come
     # from the toolchain that produced the bytes.
     def brightness(path)
-      value = `magick identify -format '%[fx:mean]' #{path.shellescape} 2>/dev/null`
+      value = `#{IDENTIFY.shelljoin} -format '%[fx:mean]' #{path.shellescape} 2>/dev/null`
       skip "ImageMagick is not installed" if value.empty?
 
       Float(value)

activestorage-hotcell-server/test/test_helper.rb

@@ -20,6 +20,9 @@
 class ActiveStorageHotCellTest < Minitest::Test
   FIXTURES = File.expand_path("fixtures", __dir__)
 
+  # ImageMagick 7 runs `magick identify`; ImageMagick 6 has `identify` and no `magick`.
+  IDENTIFY = system("magick", "-version", out: File::NULL, err: File::NULL) ? %w[ magick identify ] : %w[ identify ]
+
   private
     def fixture(name)
       File.join FIXTURES, name
@@ -51,7 +54,7 @@ def assert_failed(code, response, cause: nil)
     # One line per frame, and a format string is repeated once per frame too — which is how the first version of
     # this read a frame count out of the wrong token and blamed the operation for it.
     def identify(path)
-      lines = `magick identify -format '%w %h %m\n' #{path.shellescape} 2>/dev/null`.lines
+      lines = `#{IDENTIFY.shelljoin} -format '%w %h %m\n' #{path.shellescape} 2>/dev/null`.lines
       skip "ImageMagick is not installed" if lines.empty?
 
       width, height, format = lines.first.split