add readme

acceptance/daemon/child-detaches/script

@@ -7,3 +7,15 @@ echo -n "[script]"
 wait_pid $(cat ./child.pid)
 
 rm ./child.pid
+
+# README:
+# This test validates two features of libs/daemon:
+# 1. The parent process does not wait for the child process to end.
+# 2. The child process correctly receives input from the parent process.
+#
+# Property (1) is validated because the child process waits for it's parent process
+# to end before it writes to stdout.
+#
+# Property (2) is directly validated by the output of the child process.
+#
+# See the code for "selftest parent" and "selftest child" commands for more details.

acceptance/daemon/child-discards-output/script

@@ -7,3 +7,7 @@ wait_pid $(cat ./child.pid)
 echo "[script] child process should not have written any output."
 
 rm ./child.pid
+
+# README:
+# THis test validates that stdout / stderr from the child process are not leaked
+# to the parent process's output.