Make ./mk/run-test.sh work by itself; add mk/debug-test.sh

First, logic is consolidated in the shell script instead of being spread
between them and makefiles. That makes understanding what is going on a
little easier.

This would not be super interesting by itself, but it gives us a way to
debug tests more easily. *That* in turn I hope is much more compelling.
See the updated manual for details.

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
Co-authored-by: Eelco Dolstra <edolstra@gmail.com>
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>

mk/common-test.sh

@@ -0,0 +1,11 @@
+TESTS_ENVIRONMENT=("TEST_NAME=${test%.*}" 'NIX_REMOTE=')
+
+: ${BASH:=/usr/bin/env bash}
+
+init_test () {
+   cd tests && env "${TESTS_ENVIRONMENT[@]}" $BASH -e init.sh 2>/dev/null > /dev/null
+}
+
+run_test_proper () {
+   cd $(dirname $test) && env "${TESTS_ENVIRONMENT[@]}" $BASH -e $(basename $test)
+}

mk/debug-test.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+set -eu
+
+test=$1
+
+dir="$(dirname "${BASH_SOURCE[0]}")"
+source "$dir/common-test.sh"
+
+(init_test)
+run_test_proper

mk/run-test.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 set -u
 
@@ -7,7 +7,12 @@ green=""
 yellow=""
 normal=""
 
-post_run_msg="ran test $1..."
+test=$1
+
+dir="$(dirname "${BASH_SOURCE[0]}")"
+source "$dir/common-test.sh"
+
+post_run_msg="ran test $test..."
 if [ -t 1 ]; then
     red=""
     green=""
@@ -16,12 +21,12 @@ if [ -t 1 ]; then
 fi
 
 run_test () {
-    (cd tests && env ${TESTS_ENVIRONMENT} init.sh 2>/dev/null > /dev/null)
-    log="$(cd $(dirname $1) && env ${TESTS_ENVIRONMENT} $(basename $1) 2>&1)"
+    (init_test 2>/dev/null > /dev/null)
+    log="$(run_test_proper 2>&1)"
     status=$?
 }
 
-run_test "$1"
+run_test
 
 # Hack: Retry the test if it fails with “unexpected EOF reading a line” as these
 # appear randomly without anyone knowing why.
@@ -32,7 +37,7 @@ if [[ $status -ne 0 && $status -ne 99 && \
 ]]; then
     echo "$post_run_msg [${yellow}FAIL$normal] (possibly flaky, so will be retried)"
     echo "$log" | sed 's/^/    /'
-    run_test "$1"
+    run_test
 fi
 
 if [ $status -eq 0 ]; then

mk/tests.mk

@@ -8,7 +8,11 @@ define run-install-test
 
   .PHONY: $1.test
   $1.test: $1 $(test-deps)
-	@env TEST_NAME=$(basename $1) TESTS_ENVIRONMENT="$(tests-environment)" mk/run_test.sh $1 < /dev/null
+	@env BASH=$(bash) $(bash) mk/run-test.sh $1 < /dev/null
+
+  .PHONY: $1.test-debug
+  $1.test-debug: $1 $(test-deps)
+	@env BASH=$(bash) $(bash) mk/debug-test.sh $1 < /dev/null
 
 endef