Add test to check that promql.FunctionCalls and parser.Functions contain the same functions

Signed-off-by: Tobias Guggenmos <tguggenm@redhat.com>

promql/functions_test.go

@@ -15,11 +15,13 @@ package promql
 
 import (
 	"context"
+	"fmt"
 	"testing"
 	"time"
 
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/pkg/timestamp"
+	"github.com/prometheus/prometheus/promql/parser"
 	"github.com/prometheus/prometheus/util/teststorage"
 	"github.com/prometheus/prometheus/util/testutil"
 )
@@ -56,3 +58,24 @@ func TestDeriv(t *testing.T) {
 	testutil.Assert(t, len(vec) == 1, "Expected 1 result, got %d", len(vec))
 	testutil.Assert(t, vec[0].V == 0.0, "Expected 0.0 as value, got %f", vec[0].V)
 }
+
+func TestFunctionList(t *testing.T) {
+	// Test that Functions and parser.Functions list the same functions
+	for i := range FunctionCalls {
+		_, ok := parser.Functions[i]
+
+		if !ok {
+			panic(fmt.Sprintf("function %s exists in promql package, but not in parser package", i))
+		}
+
+	}
+
+	for i := range parser.Functions {
+		_, ok := FunctionCalls[i]
+
+		if !ok {
+			panic(fmt.Sprintf("function %s exists in promql package, but not in parser package", i))
+		}
+
+	}
+}