Intercept most exit calls and raise instead

src/spectator/includes.cr

@@ -51,6 +51,7 @@ require "./runner_events"
 require "./runner"
 require "./spec_builder"
 require "./spec"
+require "./system_exit"
 require "./tag_node_filter"
 require "./test_context"
 require "./value"

src/spectator/system_exit.cr

@@ -0,0 +1,25 @@
+module Spectator
+  # Indicates a call to exit the application was performed.
+  class SystemExit < Exception
+    # Status code passed to the exit call.
+    getter status : Int32
+
+    # Creates the exception.
+    def initialize(message : String? = nil, cause : Exception? = nil, @status : Int32 = 0)
+      super(message, cause)
+    end
+  end
+
+  # Allow Spectator to exit normally when needed.
+  private def self.exit(status = 0) : NoReturn
+    ::Crystal::System::Process.exit(status)
+  end
+end
+
+class Process
+  # Replace the typically used exit method with a method that raises.
+  # This allows tests to catch attempts to exit the application.
+  def self.exit(status = 0) : NoReturn
+    raise ::Spectator::SystemExit.new(status: status)
+  end
+end