Add zaptest.observer.(*ObservedLogs).FilterLevelExact

Method `observer.(*ObservedLogs).FilterLevelExact` allows consumers to select
entries logged at a given level, for testing.

zaptest/observer/observer.go

@@ -78,6 +78,13 @@ func (o *ObservedLogs) AllUntimed() []LoggedEntry {
 	return ret
 }
 
+// FilterLevelExact filters entries to those logged at exactly the given level.
+func (o *ObservedLogs) FilterLevelExact(level zapcore.Level) *ObservedLogs {
+	return o.Filter(func(e LoggedEntry) bool {
+		return e.Level == level
+	})
+}
+
 // FilterMessage filters entries to those that have the specified message.
 func (o *ObservedLogs) FilterMessage(msg string) *ObservedLogs {
 	return o.Filter(func(e LoggedEntry) bool {

zaptest/observer/observer_test.go

@@ -157,6 +157,14 @@ func TestFilters(t *testing.T) {
 			Entry:   zapcore.Entry{Level: zap.InfoLevel, Message: "any slice"},
 			Context: []zapcore.Field{zap.Any("filterMe", []string{"b"})},
 		},
+		{
+			Entry:   zapcore.Entry{Level: zap.WarnLevel, Message: "danger will robinson"},
+			Context: []zapcore.Field{zap.Int("b", 42)},
+		},
+		{
+			Entry:   zapcore.Entry{Level: zap.ErrorLevel, Message: "warp core breach"},
+			Context: []zapcore.Field{zap.Int("b", 42)},
+		},
 	}
 
 	logger, sink := New(zap.InfoLevel)
@@ -232,6 +240,11 @@ func TestFilters(t *testing.T) {
 				return w
 			}(),
 		},
+		{
+			msg:      "filter level",
+			filtered: sink.FilterLevelExact(zap.WarnLevel),
+			want:     logs[9:10],
+		},
 	}
 
 	for _, tt := range tests {