add tests for ratelimit stuff

Author: henrymcconville

exporter/prometheus_test.go

@@ -0,0 +1,191 @@
+package exporter
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"os"
+	"testing"
+
+	"github.com/githubexporter/github-exporter/config"
+	"github.com/google/go-github/v76/github"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// writeTempRSAKey generates a 2048-bit RSA private key and writes it as a
+// PKCS#1 PEM file to a temp path. The file is removed automatically when the
+// test finishes.
+func writeTempRSAKey(t *testing.T) string {
+	t.Helper()
+	key, err := rsa.GenerateKey(rand.Reader, 2048)
+	require.NoError(t, err)
+
+	f, err := os.CreateTemp("", "test-github-app-key-*.pem")
+	require.NoError(t, err)
+	defer f.Close()
+
+	err = pem.Encode(f, &pem.Block{
+		Type:  "RSA PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(key),
+	})
+	require.NoError(t, err)
+	t.Cleanup(func() { os.Remove(f.Name()) })
+	return f.Name()
+}
+
+func newTestExporter(cfg config.Config) *Exporter {
+	return &Exporter{
+		Client: github.NewClient(nil),
+		Config: cfg,
+	}
+}
+
+func TestRateLimitRefresh(t *testing.T) {
+	// Shared rate-limit slices used across sub-tests.
+	aboveThreshold := []RateLimit{{Resource: "core", Remaining: 200, Limit: 5000}}
+	atThreshold := []RateLimit{{Resource: "core", Remaining: 100, Limit: 5000}}
+	belowThreshold := []RateLimit{{Resource: "core", Remaining: 50, Limit: 5000}}
+	noCoreEntry := []RateLimit{{Resource: "search", Remaining: 5, Limit: 30}}
+
+	baseCfg := config.Config{
+		GitHubResultsPerPage:     100,
+		FetchReposConcurrency:    1,
+		FetchOrgsConcurrency:     1,
+		FetchOrgReposConcurrency: 1,
+		FetchUsersConcurrency:    1,
+	}
+
+	t.Run("no-op when GitHubRateLimit is zero", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 0
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&atThreshold)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("no-op when GitHubRateLimit is negative", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = -1
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&atThreshold)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("no-op when rates is nil", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(nil)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("no-op when core remaining is above threshold", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100 // remaining=200 > threshold=100
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&aboveThreshold)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("no-op when rates has no core entry", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&noCoreEntry)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("no-op when GitHubApp is false and core is at threshold", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100 // remaining=100 <= threshold=100
+		cfg.GitHubApp = false
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&atThreshold)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("no-op when GitHubApp is false and core is below threshold", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100 // remaining=50 < threshold=100
+		cfg.GitHubApp = false
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&belowThreshold)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("no-op when GitHubApp is true but GetClient fails", func(t *testing.T) {
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100
+		cfg.GitHubApp = true
+		cfg.GitHubAppConfig = &config.GitHubAppConfig{
+			GitHubAppKeyPath:        "/nonexistent/key.pem",
+			GitHubAppId:             1,
+			GitHubAppInstallationId: 1,
+		}
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&atThreshold)
+
+		assert.Same(t, original, e.Client)
+	})
+
+	t.Run("replaces client when GitHubApp is true and core is at threshold", func(t *testing.T) {
+		keyPath := writeTempRSAKey(t)
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100 // remaining=100 <= threshold=100
+		cfg.GitHubApp = true
+		cfg.GitHubAppConfig = &config.GitHubAppConfig{
+			GitHubAppKeyPath:        keyPath,
+			GitHubAppId:             1,
+			GitHubAppInstallationId: 1,
+		}
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&atThreshold)
+
+		assert.NotSame(t, original, e.Client, "expected client to be replaced after rate limit refresh")
+	})
+
+	t.Run("replaces client when GitHubApp is true and core is below threshold", func(t *testing.T) {
+		keyPath := writeTempRSAKey(t)
+		cfg := baseCfg
+		cfg.GitHubRateLimit = 100 // remaining=50 < threshold=100
+		cfg.GitHubApp = true
+		cfg.GitHubAppConfig = &config.GitHubAppConfig{
+			GitHubAppKeyPath:        keyPath,
+			GitHubAppId:             1,
+			GitHubAppInstallationId: 1,
+		}
+		e := newTestExporter(cfg)
+		original := e.Client
+
+		e.rateLimitRefresh(&belowThreshold)
+
+		assert.NotSame(t, original, e.Client, "expected client to be replaced after rate limit refresh")
+	})
+}