Extract fake Prometheus client impl

This extracts the fake prometheus client for use across different tests.

pkg/client/fake/client.go

@@ -0,0 +1,77 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fake
+
+import (
+	"context"
+	"fmt"
+
+	prom "github.com/directxman12/k8s-prometheus-adapter/pkg/client"
+	pmodel "github.com/prometheus/common/model"
+)
+
+// FakePrometheusClient is a fake instance of prom.Client
+type FakePrometheusClient struct {
+	// AcceptableInterval is the interval in which to return queries
+	AcceptableInterval pmodel.Interval
+	// ErrQueries are queries that result in an error (whether from Query or Series)
+	ErrQueries map[prom.Selector]error
+	// Series are non-error responses to partial Series calls
+	SeriesResults map[prom.Selector][]prom.Series
+	// QueryResults are non-error responses to Query
+	QueryResults map[prom.Selector]prom.QueryResult
+}
+
+func (c *FakePrometheusClient) Series(_ context.Context, interval pmodel.Interval, selectors ...prom.Selector) ([]prom.Series, error) {
+	if (interval.Start != 0 && interval.Start < c.AcceptableInterval.Start) || (interval.End != 0 && interval.End > c.AcceptableInterval.End) {
+		return nil, fmt.Errorf("interval [%v, %v] for query is outside range [%v, %v]", interval.Start, interval.End, c.AcceptableInterval.Start, c.AcceptableInterval.End)
+	}
+	res := []prom.Series{}
+	for _, sel := range selectors {
+		if err, found := c.ErrQueries[sel]; found {
+			return nil, err
+		}
+		if series, found := c.SeriesResults[sel]; found {
+			res = append(res, series...)
+		}
+	}
+
+	return res, nil
+}
+
+func (c *FakePrometheusClient) Query(_ context.Context, t pmodel.Time, query prom.Selector) (prom.QueryResult, error) {
+	if t < c.AcceptableInterval.Start || t > c.AcceptableInterval.End {
+		return prom.QueryResult{}, fmt.Errorf("time %v for query is outside range [%v, %v]", t, c.AcceptableInterval.Start, c.AcceptableInterval.End)
+	}
+
+	if err, found := c.ErrQueries[query]; found {
+		return prom.QueryResult{}, err
+	}
+
+	if res, found := c.QueryResults[query]; found {
+		return res, nil
+	}
+
+	return prom.QueryResult{
+		Type:   pmodel.ValVector,
+		Vector: &pmodel.Vector{},
+	}, nil
+}
+
+func (c *FakePrometheusClient) QueryRange(_ context.Context, r prom.Range, query prom.Selector) (prom.QueryResult, error) {
+	return prom.QueryResult{}, nil
+}