diff --git a/tests/test_basic.py b/tests/test_basic.py
new file mode 100644
index 0000000..8467d3b
--- /dev/null
+++ b/tests/test_basic.py
@@ -0,0 +1,65 @@
+import time
+from random import random
+
+from interval_timer import IntervalTimer
+
+delta = 0.01
+F = False
+T = True
+
+def run(sleeps):
+    slp = 0
+    intervals = []
+    timestamps = []
+    for interval in IntervalTimer(1):
+        print(interval)
+        timestamps.append(time.time())
+        intervals.append(interval)
+        sleep = sleeps[slp]
+        slp += 1
+        if slp >= len(sleeps):
+            break
+        time.sleep(sleep)
+    # print(intervals)
+    # print(len(sleeps))
+    # print(len(intervals))
+    return intervals, timestamps
+
+def check_intervals_index(sleeps, intervals):
+    for i in range(len(sleeps)):
+        assert intervals[i].index == i
+
+def run_test(sleeps, starts, misses):
+    start = time.time()
+    intervals, timestamps = run(sleeps)
+    check_intervals_index(sleeps, intervals)
+
+    for i in range(len(sleeps)-1):
+        real_start = timestamps[i]-start
+        print(real_start)
+        assert starts[i]-delta < real_start, f"{i} {real_start} too small"
+        assert real_start < starts[i]+delta, f"{i} {real_start} too big"
+        assert intervals[i].missed is misses[i], f"{i} {sleeps[i]} missed?"
+
+def test_basic():
+    # start   0     1     2
+    starts = [0,    1,    2]
+    misses = [F,    F,    F]
+    sleeps = [0.1,  0.1,  1]
+    run_test(sleeps, starts, misses)
+
+def test_missing():
+    # start   0     1     2     3      4     5
+    starts = [0,    1,    3.1,  3.6,   4,    5]
+    misses = [F,    F,    T,    F,     F,    F]
+    sleeps = [0.5,  2.1,  0.5,  0.1,   0.4,  0.5]
+    run_test(sleeps, starts, misses)
+
+def test_accumulated_missing():
+    # start   0     1     2     3      4     5     6
+    starts = [0,    1,    2.2,  3.5,   5.1,  5.6,  6]
+    misses = [F,    F,    F,    F,     T,    F,    F]
+    sleeps = [0.5,  1.2,  1.3,  1.6,   0.5,  0.2,  0.1]
+    run_test(sleeps, starts, misses)
+
+