test: add an ergonomic way to access the test database for debugging (#19371)

Accessing the database during debugging currently requires either
spinning up a separate PostgreSQL instance or inspecting memory to
retrieve the DSN—both of which add unnecessary friction. While the test
suite already provisions a database by default, connecting to it for
manual inspection or debugging is not straightforward.

This change introduces a clearer and more accessible way to surface the
DSN during debugging sessions, allowing developers to connect to the
test database directly without relying on external infrastructure or ad
hoc methods.

Expected Usage:
1. Debug using dlv or the IDE.
2. Step through line by line and determine that a query isn't doing what
you'd expect
3. No further insight to be gained at the Go level
4. The next place to test is to connect directly to the database while
it is in the exact state that the test has produced just before running
the query
5. Rerun the test with this option enabled and your breakpoint set right
before the questionable query runs
6. Connect to the database and inspect or troubleshoot as you need to

coderd/database/dbtestutil/postgres.go

@@ -138,6 +138,7 @@ func initDefaultConnection(t TBSubset) error {
 
 type OpenOptions struct {
 	DBFrom *string
+	LogDSN bool
 }
 
 type OpenOption func(*OpenOptions)
@@ -150,9 +151,18 @@ func WithDBFrom(dbFrom string) OpenOption {
 	}
 }
 
+// WithLogDSN sets whether the DSN should be logged during testing.
+// This provides an ergonomic way to connect to test databases during debugging.
+func WithLogDSN(logDSN bool) OpenOption {
+	return func(o *OpenOptions) {
+		o.LogDSN = logDSN
+	}
+}
+
 // TBSubset is a subset of the testing.TB interface.
 // It allows to use dbtestutil.Open outside of tests.
 type TBSubset interface {
+	Name() string
 	Cleanup(func())
 	Helper()
 	Logf(format string, args ...any)
@@ -227,6 +237,11 @@ func Open(t TBSubset, opts ...OpenOption) (string, error) {
 		Port:     port,
 		DBName:   dbName,
 	}.DSN()
+
+	// Optionally log the DSN to help connect to the test database.
+	if openOptions.LogDSN {
+		_, _ = fmt.Fprintf(os.Stderr, "Connect to the database for %s using: psql '%s'\n", t.Name(), dsn)
+	}
 	return dsn, nil
 }
 

coderd/database/gen/dump/main.go

@@ -19,6 +19,10 @@ type mockTB struct {
 	cleanup []func()
 }
 
+func (*mockTB) Name() string {
+	return "mockTB"
+}
+
 func (t *mockTB) Cleanup(f func()) {
 	t.cleanup = append(t.cleanup, f)
 }