diff --git a/lib/stopwatch.c b/lib/stopwatch.c
index 185f4a32f..ce48e3981 100644
--- a/lib/stopwatch.c
+++ b/lib/stopwatch.c
@@ -245,7 +245,7 @@ stopwatch_get_stats_protected(const char *name,
         return false;
     }

-    stats->count = perf->samples;
+    stats->count = perf->n_samples;
     stats->unit = perf->units;
     stats->max = perf->max;
     stats->min = perf->min;
diff --git a/tests/automake.mk b/tests/automake.mk
index 18698ebc3..4d43af0a5 100644
--- a/tests/automake.mk
+++ b/tests/automake.mk
@@ -364,7 +364,8 @@ tests_ovstest_SOURCES = \
 	tests/test-uuid.c \
 	tests/test-bitmap.c \
 	tests/test-vconn.c \
-	tests/test-aa.c
+	tests/test-aa.c \
+	tests/test-stopwatch.c

 if !WIN32
 tests_ovstest_SOURCES += \
diff --git a/tests/library.at b/tests/library.at
index 5efbfbb7c..1e81a80be 100644
--- a/tests/library.at
+++ b/tests/library.at
@@ -251,3 +251,8 @@ AT_CLEANUP
 AT_SETUP([rcu])
 AT_CHECK([ovstest test-rcu-quiesce], [0], [])
 AT_CLEANUP
+
+AT_SETUP([stopwatch module])
+AT_CHECK([ovstest test-stopwatch], [0], [......
+], [ignore])
+AT_CLEANUP
diff --git a/tests/test-stopwatch.c b/tests/test-stopwatch.c
new file mode 100644
index 000000000..b49641cd7
--- /dev/null
+++ b/tests/test-stopwatch.c
@@ -0,0 +1,195 @@
+/*
+ * Copyright (c) 2018 Red Hat, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+#undef NDEBUG
+#include "stopwatch.h"
+#include <assert.h>
+#include <math.h>
+#include <stdio.h>
+#include "ovstest.h"
+#include "util.h"
+
+#define MAX_SAMPLES 100
+#define UNIT SW_MS
+
+struct test_data {
+    const char *name;
+    unsigned long long samples[MAX_SAMPLES];
+    size_t num_samples;
+    struct stopwatch_stats expected_stats;
+};
+
+static struct test_data data_sets[] = {
+    {
+        .name = "1-interval-zero-length",
+        .samples = { 0, 0 },
+        .num_samples = 2,
+        .expected_stats = {
+            .count = 1,
+            .unit = UNIT,
+            .max = 0,
+            .min = 0,
+            .pctl_95 = 0,
+            .ewma_50 = 0,
+            .ewma_1 = 0,
+        },
+    },
+    {
+        .name = "1-interval-unit-length",
+        .samples = { 0, 1 },
+        .num_samples = 2,
+        .expected_stats = {
+            .count = 1,
+            .unit = UNIT,
+            .max = 1,
+            .min = 1,
+            .pctl_95 = 0,
+            .ewma_50 = 1,
+            .ewma_1 = 1,
+        },
+    },
+    {
+        .name = "10-intervals-unit-length",
+        .samples = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 },
+        .num_samples = 11,
+        .expected_stats = {
+            .count = 10,
+            .unit = UNIT,
+            .max = 1,
+            .min = 1,
+            .pctl_95 = 1,
+            .ewma_50 = 1,
+            .ewma_1 = 1,
+        },
+    },
+    {
+        .name = "10-intervals-linear-growth",
+        .samples = { 1, 2, 4, 7, 11, 16, 22, 29, 37, 46, 56 },
+        .num_samples = 11,
+        .expected_stats = {
+            .count = 10,
+            .unit = UNIT,
+            .max = 10,
+            .min = 1,
+            .pctl_95 = 10.0,
+            .ewma_50 = 9.0,
+            .ewma_1 = 1.4,
+        },
+    },
+    {
+        .name = "60-intervals-unit-length",
+        .samples = { 1,  2,  3,  4,  5,  6,  7,  8,  9, 10,
+                    11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
+                    21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
+                    31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+                    41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
+                    51, 52, 53, 54, 55, 56, 57, 58, 59, 60,
+                    61, },
+        .num_samples = 61,
+        .expected_stats = {
+            .count = 60,
+            .unit = UNIT,
+            .max = 1,
+            .min = 1,
+            .pctl_95 = 1,
+            .ewma_50 = 1,
+            .ewma_1 = 1,
+        },
+    },
+    {
+        .name = "60-intervals-linear-growth",
+        .samples = {   1,    2,    4,    7,   11,   16,   22,   29,   37,   46,
+                      56,   67,   79,   92,  106,  121,  137,  154,  172,  191,
+                     211,  232,  254,  277,  301,  326,  352,  379,  407,  436,
+                     466,  497,  529,  562,  596,  631,  667,  704,  742,  781,
+                     821,  862,  904,  947,  991, 1036, 1082, 1129, 1177, 1226,
+                    1276, 1327, 1379, 1432, 1486, 1541, 1597, 1654, 1712, 1771,
+                    1831, },
+        .num_samples = 61,
+        .expected_stats = {
+            .count = 60,
+            .unit = UNIT,
+            .max = 60,
+            .min = 1,
+            /* 95th percentile is actually closer to 57, but the estimate is
+             * pretty dang close */
+            .pctl_95 = 56,
+            .ewma_50 = 59,
+            .ewma_1 = 15.7,
+        },
+    },
+};
+
+#define ASSERT_MSG(COND, MSG, ...)                  \
+    if (!(COND)) {                                  \
+        fprintf(stderr, MSG "\n", ##__VA_ARGS__);   \
+        assert(COND);                               \
+    }
+
+#define ASSERT_ULL_EQ(a, b)                                 \
+    ASSERT_MSG(a == b,                                      \
+               "Assertion '%s == %s' failed: %llu == %llu", \
+               #a, #b, a, b)
+
+#define ASSERT_DOUBLE_EQ(a, b, eps)                                 \
+    ASSERT_MSG(fabs(a - b) < eps,                                   \
+               "Assertion '|%s - %s| < %s' failed: |%g - %g| < %g", \
+               #a, #b, #eps, a, b, eps)
+
+#define ASSERT_STATS_EQ(a, b)                               \
+    do {                                                    \
+        ASSERT_ULL_EQ((a)->count, (b)->count);              \
+        ASSERT_ULL_EQ((a)->max, (b)->max);                  \
+        ASSERT_ULL_EQ((a)->min, (b)->min);                  \
+        ASSERT_DOUBLE_EQ((a)->pctl_95, (b)->pctl_95, 1e-1); \
+        ASSERT_DOUBLE_EQ((a)->ewma_50, (b)->ewma_50, 1e-1); \
+        ASSERT_DOUBLE_EQ((a)->ewma_1, (b)->ewma_1, 1e-1);   \
+    } while (0)
+
+static void
+test_stopwatch_calculate_stats(void)
+{
+    struct test_data *d;
+
+    for (size_t i = 0; i < ARRAY_SIZE(data_sets); i++) {
+        d = &data_sets[i];
+
+        fprintf(stderr, "TEST '%s'\n", d->name);
+
+        stopwatch_create(d->name, UNIT);
+        for (size_t j = 0; j < d->num_samples - 1; j ++) {
+            stopwatch_start(d->name, d->samples[j]);
+            stopwatch_stop(d->name, d->samples[j + 1]);
+        }
+        stopwatch_sync();
+
+        struct stopwatch_stats stats = { 0 };
+        stopwatch_get_stats(d->name, &stats);
+        ASSERT_STATS_EQ(&stats, &d->expected_stats);
+
+        printf(".");
+    }
+}
+
+static void
+test_stopwatch_main(int argc OVS_UNUSED, char *argv[] OVS_UNUSED)
+{
+    test_stopwatch_calculate_stats();
+    printf("\n");
+}
+
+OVSTEST_REGISTER("test-stopwatch", test_stopwatch_main);
