diff --git a/message_test.go b/message_test.go
index a3780c5..9f1b303 100644
--- a/message_test.go
+++ b/message_test.go
@@ -3,6 +3,7 @@ package notmuch
 import (
 	"path"
 	"reflect"
+	"runtime"
 	"testing"
 	"time"
 )
@@ -73,6 +74,11 @@ func TestMessageReplies(t *testing.T) {
 	var count int
 	for replies.Next(msg) {
 		count++
+
+		// invoke the GC to make sure it's running smoothly.
+		if count%2 == 0 {
+			runtime.GC()
+		}
 	}
 	if want, got := 2, count; want != got {
 		t.Errorf("msg.Replies(): want %d replies got %d", want, got)
@@ -133,6 +139,11 @@ func TestMessageFilenames(t *testing.T) {
 	fns := msg.Filenames()
 	for fns.Next(&fn) {
 		count++
+
+		// invoke the GC to make sure it's running smoothly.
+		if count%2 == 0 {
+			runtime.GC()
+		}
 	}
 
 	if want, got := 2, count; want != got {
@@ -178,6 +189,9 @@ func TestMessageHeader(t *testing.T) {
 		if msg.ID() == "1258471718-6781-2-git-send-email-dottedmag@dottedmag.net" {
 			break
 		}
+
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	for _, hn := range []string{"References", "references"} {
 		if want, got := "<1258471718-6781-1-git-send-email-dottedmag@dottedmag.net>", msg.Header(hn); want != got {
@@ -203,6 +217,8 @@ func TestMessageTags(t *testing.T) {
 		if msg.ID() == "1258471718-6781-2-git-send-email-dottedmag@dottedmag.net" {
 			break
 		}
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 
 	ts := msg.Tags()
@@ -210,6 +226,8 @@ func TestMessageTags(t *testing.T) {
 	var tags []string
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -233,6 +251,8 @@ func TestMessageAddRemoveTagReadonlyDB(t *testing.T) {
 		if msg.ID() == "1258471718-6781-2-git-send-email-dottedmag@dottedmag.net" {
 			break
 		}
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 
 	ts := msg.Tags()
@@ -240,6 +260,8 @@ func TestMessageAddRemoveTagReadonlyDB(t *testing.T) {
 	var tags []string
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -276,6 +298,8 @@ func TestMessageAddRemoveTag(t *testing.T) {
 		if msg.ID() == "1258471718-6781-2-git-send-email-dottedmag@dottedmag.net" {
 			break
 		}
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 
 	ts := msg.Tags()
@@ -283,6 +307,8 @@ func TestMessageAddRemoveTag(t *testing.T) {
 	var tags []string
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -296,6 +322,8 @@ func TestMessageAddRemoveTag(t *testing.T) {
 	tags = []string{}
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", tn, "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -308,6 +336,8 @@ func TestMessageAddRemoveTag(t *testing.T) {
 	tags = []string{}
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -320,6 +350,8 @@ func TestMessageAddRemoveTag(t *testing.T) {
 	tags = []string{}
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -347,6 +379,8 @@ func TestMessageAtomic(t *testing.T) {
 		if msg.ID() == "1258471718-6781-2-git-send-email-dottedmag@dottedmag.net" {
 			break
 		}
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 
 	ts := msg.Tags()
@@ -354,6 +388,8 @@ func TestMessageAtomic(t *testing.T) {
 	var tags []string
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -369,6 +405,8 @@ func TestMessageAtomic(t *testing.T) {
 	tags = []string{}
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", tn, "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
@@ -383,6 +421,8 @@ func TestMessageAtomic(t *testing.T) {
 	tags = []string{}
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("msg.Tags(): want %v got %v", want, got)
diff --git a/query_test.go b/query_test.go
index f45f13b..2b39005 100644
--- a/query_test.go
+++ b/query_test.go
@@ -4,7 +4,10 @@ package notmuch
 // Licensed under the GPLv3 or later.
 // See COPYING at the root of the repository for details.
 
-import "testing"
+import (
+	"runtime"
+	"testing"
+)
 
 func TestSearchThreads(t *testing.T) {
 	db, err := Open(dbPath, DBReadOnly)
@@ -22,6 +25,10 @@ func TestSearchThreads(t *testing.T) {
 	thread := &Thread{}
 	for threads.Next(thread) {
 		count++
+		// invoke the GC to make sure it's running smoothly.
+		if count%2 == 0 {
+			runtime.GC()
+		}
 	}
 
 	if want, got := 24, count; want != got {
@@ -45,6 +52,10 @@ func TestGetNoResult(t *testing.T) {
 	thread := &Thread{}
 	for threads.Next(thread) {
 		count++
+		// invoke the GC to make sure it's running smoothly.
+		if count%2 == 0 {
+			runtime.GC()
+		}
 	}
 
 	if want, got := 0, count; want != got {
diff --git a/thread_test.go b/thread_test.go
index 4f89e3b..9bfe5e6 100644
--- a/thread_test.go
+++ b/thread_test.go
@@ -7,6 +7,7 @@ package notmuch
 import (
 	"errors"
 	"reflect"
+	"runtime"
 	"testing"
 	"time"
 )
@@ -88,6 +89,10 @@ func TestTopLevelMessages(t *testing.T) {
 	var count int
 	for msgs.Next(message) {
 		count++
+		// invoke the GC to make sure it's running smoothly.
+		if count%2 == 0 {
+			runtime.GC()
+		}
 	}
 	if want, got := 1, count; want != got {
 		t.Errorf("db.NewQuery(%q).Threads()[0].TopLevelMessages(): want %d got %d", qs, want, got)
@@ -114,6 +119,10 @@ func TestMessages(t *testing.T) {
 	var count int
 	for msgs.Next(message) {
 		count++
+		// invoke the GC to make sure it's running smoothly.
+		if count%2 == 0 {
+			runtime.GC()
+		}
 	}
 	if want, got := 3, count; want != got {
 		t.Errorf("db.NewQuery(%q).Threads()[0].Messages(): want %d got %d", qs, want, got)
@@ -168,6 +177,11 @@ func TestAuthors(t *testing.T) {
 			if want, got := ress[i].unmatched, unmatched; !reflect.DeepEqual(want, got) {
 				t.Errorf("thread.Authors() unmatched: want %v got %v", want, got)
 			}
+
+			// invoke the GC to make sure it's running smoothly.
+			if i%2 == 0 {
+				runtime.GC()
+			}
 		}
 	}
 }
@@ -223,6 +237,8 @@ func TestThreadTags(t *testing.T) {
 	var tags []string
 	for ts.Next(tag) {
 		tags = append(tags, tag.Value)
+		// invoke the GC to make sure it's running smoothly.
+		runtime.GC()
 	}
 	if want, got := []string{"inbox", "signed", "unread"}, tags; !reflect.DeepEqual(want, got) {
 		t.Errorf("thread.Tags(): want %v got %v", want, got)