JUnit reporter uses only 3 decimal places when reporting durations

We used to use whatever precision we ended up having from C++'s
stdlib. However, some relatively popular tools, like Jenkins,
use Maven SureFire XML schema to validate JUnit test reports, and
Maven SureFire schema requires the duration to have at most 3
decimal places.

For compatibility, the JUnit reporter will now respect this
limitation.

Closes #2221

src/catch2/reporters/catch_reporter_junit.cpp

@@ -17,6 +17,7 @@
 #include <cassert>
 #include <ctime>
 #include <algorithm>
+#include <iomanip>
 
 namespace Catch {
 
@@ -54,6 +55,17 @@ namespace Catch {
             }
             return std::string();
         }
+
+        // Formats the duration in seconds to 3 decimal places.
+        // This is done because some genius defined Maven Surefire schema
+        // in a way that only accepts 3 decimal places, and tools like
+        // Jenkins use that schema for validation JUnit reporter output.
+        std::string formatDuration( double seconds ) {
+            ReusableStringStream rss;
+            rss << std::fixed << std::setprecision( 3 ) << seconds;
+            return rss.str();
+        }
+
     } // anonymous namespace
 
     JunitReporter::JunitReporter( ReporterConfig const& _config )
@@ -111,7 +123,7 @@ namespace Catch {
         if( m_config->showDurations() == ShowDurations::Never )
             xml.writeAttribute( "time"_sr, ""_sr );
         else
-            xml.writeAttribute( "time"_sr, suiteTime );
+            xml.writeAttribute( "time"_sr, formatDuration( suiteTime ) );
         xml.writeAttribute( "timestamp"_sr, getCurrentTimestamp() );
 
         // Write properties
@@ -178,7 +190,7 @@ namespace Catch {
                 xml.writeAttribute( "classname"_sr, className );
                 xml.writeAttribute( "name"_sr, name );
             }
-            xml.writeAttribute( "time"_sr, ::Catch::Detail::stringify( sectionNode.stats.durationInSeconds ) );
+            xml.writeAttribute( "time"_sr, formatDuration( sectionNode.stats.durationInSeconds ) );
             // This is not ideal, but it should be enough to mimic gtest's
             // junit output.
             // Ideally the JUnit reporter would also handle `skipTest`

tools/scripts/approvalTests.py

@@ -29,7 +29,11 @@ filelocParser = re.compile(r'''
 lineNumberParser = re.compile(r' line="[0-9]*"')
 hexParser = re.compile(r'\b(0[xX][0-9a-fA-F]+)\b')
 durationsParser = re.compile(r' time="[0-9]*\.[0-9]*"')
-sonarqubeDurationParser = re.compile(r''' duration=["'][0-9]+["']''')
+# Note: junit must serialize time with 3 (or or less) decimal places
+#       before generalizing this parser, make sure that this is checked
+#       in other places too.
+junitDurationsParser = re.compile(r' time="[0-9]+\.[0-9]{3}"')
+durationParser = re.compile(r''' duration=['"][0-9]+['"]''')
 timestampsParser = re.compile(r'\d{4}-\d{2}-\d{2}T\d{2}\:\d{2}\:\d{2}Z')
 versionParser = re.compile(r'Catch v[0-9]+\.[0-9]+\.[0-9]+(-\w*\.[0-9]+)?')
 nullParser = re.compile(r'\b(__null|nullptr)\b')
@@ -143,8 +147,8 @@ def filterLine(line, isCompact):
     line = hexParser.sub("0x<hex digits>", line)
 
     # strip durations and timestamps
-    line = durationsParser.sub(' time="{duration}"', line)
+    line = junitDurationsParser.sub(' time="{duration}"', line)
-    line = sonarqubeDurationParser.sub(' duration="{duration}"', line)
+    line = durationParser.sub(' duration="{duration}"', line)
     line = timestampsParser.sub('{iso8601-timestamp}', line)
     line = specialCaseParser.sub('file:\g<1>', line)
     line = errnoParser.sub('errno', line)