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// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
// SPDX-License-Identifier: Apache-2.0
package microprom_test
import (
"context"
"errors"
"io"
"maps"
"net/http"
"net/http/httptest"
"strings"
"testing"
"go.xyrillian.de/gg/assert"
"go.xyrillian.de/gg/microprom"
)
func TestHandlerBasic(t *testing.T) {
// NOTE: Most happy path coverage is in `./testing/microprom`.
// This only covers the SortOutput = false case.
h := microprom.Handler{
Families: map[microprom.MetricFamilyName]microprom.MetricFamilyInfo{
"process": {
Type: microprom.MetricTypeInfo,
Help: "Information about this process.",
},
"foo": {
Type: microprom.MetricTypeGauge,
Help: "This metric family will not have any collected metrics and thus go unreported.",
},
},
Collect: func(ctx context.Context, ms *microprom.MetricSet) error {
names := microprom.NewLabelNames("version")
labels := ms.FormatLabels(names, "1.2.3")
ms.Add("process", labels, 1.0)
return nil
},
}
// test normal behavior
status, body, headers := getMetrics(t, h, nil)
assert.Equal(t, status, http.StatusOK)
assert.Equal(t, headers, http.Header{
"Content-Type": {"text/plain; version=0.0.4; charset=utf-8; escaping=underscores"},
})
assert.Equal(t, body, strings.TrimSpace(`
# HELP process_info Information about this process.
# TYPE process_info info
process_info{version="1.2.3"} 1
`)+"\n")
}
func TestHandlerErrors(t *testing.T) {
h := microprom.Handler{
Families: map[microprom.MetricFamilyName]microprom.MetricFamilyInfo{
"process": {
Type: microprom.MetricTypeInfo,
Help: "Information about this process.",
},
},
Collect: func(ctx context.Context, ms *microprom.MetricSet) error {
return errors.New("kaboom")
},
}
// test unacceptable content negotiation
status, body, headers := getMetrics(t, h, http.Header{"Accept": {"application/json"}})
assert.Equal(t, status, http.StatusNotAcceptable)
assert.Equal(t, headers.Get("Content-Type"), "text/plain; charset=utf-8")
assert.Equal(t, body, "supported formats are text/plain and application/openmetrics-text\n")
// test error during h.Collect()
status, body, headers = getMetrics(t, h, nil)
assert.Equal(t, status, http.StatusInternalServerError)
assert.Equal(t, headers.Get("Content-Type"), "text/plain; charset=utf-8")
assert.Equal(t, body, "kaboom\n")
// test panic from invalid metric family name
h.Families["what is this?"] = microprom.MetricFamilyInfo{
Type: microprom.MetricTypeGauge,
Help: "invalid metric family name",
}
msg := assert.PanicsWith[string](t, func() { getMetrics(t, h, nil) })
assert.Equal(t, msg, `in family "what is this?": invalid family name (does not match /^[a-zA-Z_:][a-zA-Z0-9_:]*$/)`)
delete(h.Families, "what is this?")
// test panic from invalid metric type
h.Families["invalid"] = microprom.MetricFamilyInfo{
Type: 100,
Help: "invalid metric type",
}
msg = assert.PanicsWith[string](t, func() { getMetrics(t, h, nil) })
assert.Equal(t, msg, `in family "invalid": invalid value for microprom.MetricType: 100`)
delete(h.Families, "invalid")
// test panic from invalid label name
h.Collect = func(ctx context.Context, ms *microprom.MetricSet) error {
names := microprom.NewLabelNames("app:version")
labels := ms.FormatLabels(names, "1.2.3")
ms.Add("process", labels, 1.0)
return nil
}
msg = assert.PanicsWith[string](t, func() { getMetrics(t, h, nil) })
assert.Equal(t, msg, `invalid label name: "app:version"`)
// test panic from wrong number of label values
h.Collect = func(ctx context.Context, ms *microprom.MetricSet) error {
names := microprom.NewLabelNames("version", "build_date")
labels := ms.FormatLabels(names, "1.2.3") // forgot build_date
ms.Add("process", labels, 1.0)
return nil
}
msg = assert.PanicsWith[string](t, func() { getMetrics(t, h, nil) })
assert.Equal(t, msg, `expected 2 label values, but got 1`)
// test panic from using an undeclared metric family
h.Collect = func(ctx context.Context, ms *microprom.MetricSet) error {
ms.Add("invalid", "", 1.0)
return nil
}
msg = assert.PanicsWith[string](t, func() { getMetrics(t, h, nil) })
assert.Equal(t, msg, `no such family: invalid`)
}
func getMetrics(t *testing.T, h http.Handler, requestHeaders http.Header) (status int, responseBody string, responseHeaders http.Header) {
t.Helper()
r := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/metrics", nil)
maps.Copy(r.Header, requestHeaders)
w := httptest.NewRecorder()
h.ServeHTTP(w, r)
resp := w.Result()
buf, err := io.ReadAll(resp.Body)
if err != nil {
t.Fatal(err.Error())
}
return resp.StatusCode, string(buf), resp.Header
}
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