Add first set of tests + some helper functions cribbed from

mysqld_exporter

Signed-off-by: Felix Yuan <[email protected]>

Author: Sticksman

collector/pg_database.go

@@ -47,6 +47,9 @@ var pgDatabaseSizeBytes = prometheus.NewDesc(
 	[]string{"datname"}, nil,
 )
 
+var pgDatabaseQuery = "SELECT pg_database.datname FROM pg_database;"
+var pgDatabaseSizeQuery = "SELECT pg_database_size($1)"
+
 // Update implements Collector and exposes database size.
 // It is called by the Prometheus registry when collecting metrics.
 // The list of databases is retrieved from pg_database and filtered
@@ -58,9 +61,7 @@ var pgDatabaseSizeBytes = prometheus.NewDesc(
 func (c PGDatabaseCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
 	// Query the list of databases
 	rows, err := db.QueryContext(ctx,
-		`SELECT pg_database.datname
-		FROM pg_database;
-		`,
+		pgDatabaseQuery,
 	)
 	if err != nil {
 		return err
@@ -88,7 +89,7 @@ func (c PGDatabaseCollector) Update(ctx context.Context, db *sql.DB, ch chan<- p
 	// Query the size of the databases
 	for _, datname := range databases {
 		var size int64
-		err = db.QueryRowContext(ctx, "SELECT pg_database_size($1)", datname).Scan(&size)
+		err = db.QueryRowContext(ctx, pgDatabaseSizeQuery, datname).Scan(&size)
 		if err != nil {
 			return err
 		}

go.mod

@@ -3,6 +3,7 @@ module github.com/prometheus-community/postgres_exporter
 go 1.19
 
 require (
+	github.com/DATA-DOG/go-sqlmock v1.5.0
 	github.com/alecthomas/kingpin/v2 v2.3.2
 	github.com/blang/semver/v4 v4.0.0
 	github.com/go-kit/log v0.2.1
@@ -23,13 +24,17 @@ require (
 	github.com/coreos/go-systemd/v22 v22.5.0 // indirect
 	github.com/go-logfmt/logfmt v0.5.1 // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
+	github.com/gopherjs/gopherjs v1.17.2 // indirect
 	github.com/jpillora/backoff v1.0.0 // indirect
+	github.com/jtolds/gls v4.20.0+incompatible // indirect
 	github.com/kr/pretty v0.3.1 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
 	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f // indirect
 	github.com/prometheus/procfs v0.9.0 // indirect
 	github.com/rogpeppe/go-internal v1.9.0 // indirect
+	github.com/smartystreets/assertions v1.13.1 // indirect
+	github.com/smartystreets/goconvey v1.8.0 // indirect
 	github.com/xhit/go-str2duration/v2 v2.1.0 // indirect
 	golang.org/x/crypto v0.7.0 // indirect
 	golang.org/x/net v0.8.0 // indirect

go.sum

@@ -1,3 +1,5 @@
+github.com/DATA-DOG/go-sqlmock v1.5.0 h1:Shsta01QNfFxHCfpW6YH2STWB0MudeXXEWMr20OEh60=
+github.com/DATA-DOG/go-sqlmock v1.5.0/go.mod h1:f/Ixk793poVmq4qj/V1dPUg2JEAKC73Q5eFN3EC/SaM=
 github.com/alecthomas/kingpin/v2 v2.3.2 h1:H0aULhgmSzN8xQ3nX1uxtdlTHYoPLu5AhHxWrKI6ocU=
 github.com/alecthomas/kingpin/v2 v2.3.2/go.mod h1:0gyi0zQnjuFk8xrkNKamJoyUo382HRL7ATRpFZCw6tE=
 github.com/alecthomas/units v0.0.0-20211218093645-b94a6e3cc137 h1:s6gZFSlWYmbqAuRjVTiNNhvNRfY2Wxp9nhfyel4rklc=
@@ -26,8 +28,12 @@ github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw
 github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38=
+github.com/gopherjs/gopherjs v1.17.2 h1:fQnZVsXk8uxXIStYb0N4bGk7jeyTalG/wsZjQ25dO0g=
+github.com/gopherjs/gopherjs v1.17.2/go.mod h1:pRRIvn/QzFLrKfvEz3qUuEhtE/zLCWfreZ6J5gM2i+k=
 github.com/jpillora/backoff v1.0.0 h1:uvFg412JmmHBHw7iwprIxkPMI+sGQ4kzOWsMeHnm2EA=
 github.com/jpillora/backoff v1.0.0/go.mod h1:J/6gKK9jxlEcS3zixgDgUAsiuZ7yrSoa/FX5e0EB2j4=
+github.com/jtolds/gls v4.20.0+incompatible h1:xdiiI2gbIgH/gLH7ADydsJ1uDOEzR8yvV7C0MuV77Wo=
+github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
 github.com/kr/pretty v0.2.1/go.mod h1:ipq/a2n7PKx3OHsz4KJII5eveXtPO4qwEXGdVfWzfnI=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
@@ -56,6 +62,10 @@ github.com/prometheus/procfs v0.9.0 h1:wzCHvIvM5SxWqYvwgVL7yJY8Lz3PKn49KQtpgMYJf
 github.com/prometheus/procfs v0.9.0/go.mod h1:+pB4zwohETzFnmlpe6yd2lSc+0/46IYZRB/chUwxUZY=
 github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
+github.com/smartystreets/assertions v1.13.1 h1:Ef7KhSmjZcK6AVf9YbJdvPYG9avaF0ZxudX+ThRdWfU=
+github.com/smartystreets/assertions v1.13.1/go.mod h1:cXr/IwVfSo/RbCSPhoAPv73p3hlSdrBH/b3SdnW/LMY=
+github.com/smartystreets/goconvey v1.8.0 h1:Oi49ha/2MURE0WexF052Z0m+BNSGirfjg5RL+JXWq3w=
+github.com/smartystreets/goconvey v1.8.0/go.mod h1:EdX8jtrTIj26jmjCOVNMVSIYAtgexqXKHOXW2Dx9JLg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=