Add error source (#1954)

Fixes  #1879

pkg/datasource/functions_test.go

@@ -0,0 +1,128 @@
+package datasource
+
+import (
+	"testing"
+	"time"
+
+	"github.com/alexanderzobnin/grafana-zabbix/pkg/timeseries"
+	"github.com/alexanderzobnin/grafana-zabbix/pkg/zabbix"
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestApplyFunctionsFunction(t *testing.T) {
+	f := new(float64)
+	*f = 1.0
+	series := []*timeseries.TimeSeriesData{
+		{
+			TS: timeseries.TimeSeries{
+				{Time: time.Time{}, Value: f},
+				{Time: time.Time{}, Value: f},
+			},
+		},
+	}
+
+	tests := []struct {
+		name      string
+		functions []QueryFunction
+		wantErr   bool
+	}{
+		{
+			name: "unsupported function",
+			functions: []QueryFunction{
+				{
+					Def: QueryFunctionDef{
+						Name: "unsupportedFunction",
+					},
+					Params: []interface{}{},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "data processing function with params error",
+			functions: []QueryFunction{
+				{
+					Def: QueryFunctionDef{
+						Name: "groupBy",
+					},
+					Params: []interface {
+					}{1},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "aggregate function with params error",
+			functions: []QueryFunction{
+				{
+					Def: QueryFunctionDef{
+						Name: "aggregateBy",
+					},
+					Params: []interface {
+					}{1},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "filter function with params error",
+			functions: []QueryFunction{
+				{
+					Def: QueryFunctionDef{
+						Name: "top",
+					},
+					Params: []interface {
+					}{"string"},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "skipped function should return no error",
+			functions: []QueryFunction{
+				{
+					Def: QueryFunctionDef{
+						Name: "setAlias",
+					},
+					Params: []interface {
+					}{},
+				},
+			},
+			wantErr: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := applyFunctions(series, tt.functions)
+			if tt.wantErr {
+				assert.Error(t, err, "expected error for function")
+				// Check if the error is a downstream error
+				assert.Truef(t, backend.IsDownstreamError(err), "error is not a downstream error")
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}
+// TestApplyFunctionsPreFunction tests the applyFunctionsPre function for error handling
+func TestApplyFunctionsPreFunction(t *testing.T) {
+	query := QueryModel{
+		Functions: []QueryFunction{
+			{
+				Def: QueryFunctionDef{
+					Name: "timeShift",
+				},
+				Params: []interface{}{1},
+			},
+		}}
+
+	items := []*zabbix.Item{}
+	err := applyFunctionsPre(&query, items)
+
+	assert.Error(t, err, "expected error for function")
+	// Check if the error is a downstream error
+	assert.Truef(t, backend.IsDownstreamError(err), "error is not a downstream error")
+
+}