libtest: add tests for junit output format

I'm about to make some changes here, and it was making me uneasy to
modify the output format without test coverage.

tests/run-make/libtest-junit/Makefile

@@ -0,0 +1,19 @@
+# ignore-cross-compile
+include ../tools.mk
+
+# Test expected libtest's junit output
+
+OUTPUT_FILE_DEFAULT := $(TMPDIR)/libtest-junit-output-default.xml
+OUTPUT_FILE_STDOUT_SUCCESS := $(TMPDIR)/libtest-junit-output-stdout-success.xml
+
+all: f.rs validate_junit.py output-default.xml output-stdout-success.xml
+	$(RUSTC) --test f.rs
+	RUST_BACKTRACE=0 $(call RUN,f) -Z unstable-options --test-threads=1 --format=junit > $(OUTPUT_FILE_DEFAULT) || true
+	RUST_BACKTRACE=0 $(call RUN,f) -Z unstable-options --test-threads=1 --format=junit --show-output > $(OUTPUT_FILE_STDOUT_SUCCESS) || true
+
+	cat $(OUTPUT_FILE_DEFAULT) | "$(PYTHON)" validate_junit.py
+	cat $(OUTPUT_FILE_STDOUT_SUCCESS) | "$(PYTHON)" validate_junit.py
+
+	# Normalize the actual output and compare to expected output file
+	cat $(OUTPUT_FILE_DEFAULT) | sed 's/time="[0-9.]*"/time="$$TIME"/g' | diff output-default.xml -
+	cat $(OUTPUT_FILE_STDOUT_SUCCESS) | sed 's/time="[0-9.]*"/time="$$TIME"/g' | diff output-stdout-success.xml -

tests/run-make/libtest-junit/f.rs

@@ -0,0 +1,23 @@
+#[test]
+fn a() {
+    println!("print from successful test");
+    // Should pass
+}
+
+#[test]
+fn b() {
+    println!("print from failing test");
+    assert!(false);
+}
+
+#[test]
+#[should_panic]
+fn c() {
+    assert!(false);
+}
+
+#[test]
+#[ignore = "msg"]
+fn d() {
+    assert!(false);
+}

tests/run-make/libtest-junit/output-default.xml

@@ -0,0 +1 @@
+<?xml version="1.0" encoding="UTF-8"?><testsuites><testsuite name="test" package="test" id="0" errors="0" failures="1" tests="4" skipped="1" ><testcase classname="unknown" name="a" time="$TIME"/><testcase classname="unknown" name="b" time="$TIME"><failure type="assert"/></testcase><testcase classname="unknown" name="c" time="$TIME"/><system-out/><system-err/></testsuite></testsuites>

tests/run-make/libtest-junit/output-stdout-success.xml

@@ -0,0 +1 @@
+<?xml version="1.0" encoding="UTF-8"?><testsuites><testsuite name="test" package="test" id="0" errors="0" failures="1" tests="4" skipped="1" ><testcase classname="unknown" name="a" time="$TIME"/><testcase classname="unknown" name="b" time="$TIME"><failure type="assert"/></testcase><testcase classname="unknown" name="c" time="$TIME"/><system-out/><system-err/></testsuite></testsuites>

tests/run-make/libtest-junit/validate_junit.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env python
+
+import sys
+import xml.etree.ElementTree as ET
+
+# Try to decode line in order to ensure it is a valid XML document
+for line in sys.stdin:
+    try:
+        ET.fromstring(line)
+    except ET.ParseError as pe:
+        print("Invalid xml: %r" % line)
+        raise