Further test the override.

test/cli/main_test.rb

@@ -283,6 +283,16 @@ class CliMainTest < CliTestCase
     end
   end
 
+  test "config with primary web role override" do
+    run_command("config", config_file: "deploy_primary_web_role_override").tap do |output|
+      config = YAML.load(output)
+
+      assert_equal ["web_chicago", "web_tokyo"], config[:roles]
+      assert_equal ["1.1.1.1", "1.1.1.2", "1.1.1.3", "1.1.1.4"], config[:hosts]
+      assert_equal "1.1.1.3", config[:primary_host]
+    end
+  end
+
   test "config with destination" do
     run_command("config", "-d", "world", config_file: "deploy_for_dest").tap do |output|
       config = YAML.load(output)

test/fixtures/deploy_primary_web_role_override.yml

@@ -0,0 +1,20 @@
+service: app
+image: dhh/app
+servers:
+  web_chicago:
+    traefik: enabled
+    hosts:
+      - 1.1.1.1
+      - 1.1.1.2
+  web_tokyo:
+    traefik: enabled
+    hosts:
+      - 1.1.1.3
+      - 1.1.1.4
+env:
+  REDIS_URL: redis://x/y
+registry:
+  server: registry.digitalocean.com
+  username: user
+  password: pw
+primary_web_role: web_tokyo