Test reading fixed-layout multi-frequency signals.

This test case uses an excerpt of record mimicdb/041/, which is a
fixed-layout record with three signals at 500 Hz (four samples per
frame) and four signals at 125 Hz (one sample per frame).

Author: Benjamin Moody

sample-data/multi-segment/041s/041s.hea

@@ -0,0 +1,3 @@
+041s/2 7 125 2000 8:26:04 26/10/1994
+041s01 1000
+041s02 1000

sample-data/multi-segment/041s/041s01.dat

@@ -0,0 +1,9 @@
+041s01 7 125 1000  8:26:04 26/10/1994
+041s01.dat 212x4 2000 12 0 168 -2716 0 III 
+041s01.dat 212x4 2000 12 0 2 -25019 0 I 
+041s01.dat 212x4 2000 12 0 155 -12467 0 V 
+041s01.dat 212 20(-1600)/mmHg 12 0 -242 -18875 0 ABP 
+041s01.dat 212 80(-1600)/mmHg 12 0 706 -5338 0 PAP 
+041s01.dat 212 2000 12 0 -841 30145 0 PLETH 
+041s01.dat 212 2000 12 0 401 3712 0 RESP 
+#Produced by xform from record mimicdb/041/04100001, beginning at s74000

sample-data/multi-segment/041s/041s01.hea

@@ -0,0 +1,9 @@
+041s02 7 125 1000  8:26:12 26/10/1994
+041s02.dat 212x4 2000 12 0 -103 -862 0 III 
+041s02.dat 212x4 2000 12 0 -64 14967 0 I 
+041s02.dat 212x4 2000 12 0 89 13162 0 V 
+041s02.dat 212 20(-1600)/mmHg 12 0 -715 -21117 0 ABP 
+041s02.dat 212 80(-1600)/mmHg 12 0 -583 -31770 0 PAP 
+041s02.dat 212 2000 12 0 -840 -31041 0 PLETH 
+041s02.dat 212 2000 12 0 -861 -31272 0 RESP 
+#Produced by xform from record mimicdb/041/04100002, beginning at 0:0

sample-data/multi-segment/041s/041s02.dat

@@ -746,6 +746,41 @@ def test_multi_fixed_c(self):
         np.testing.assert_equal(sig_round, sig_target)
         assert record.__eq__(record_named)
 
+    def test_multi_fixed_d(self):
+        """
+        Multi-segment, fixed layout, multi-frequency, selected channels
+
+        Target file created with:
+            rdsamp -r sample-data/multi-segment/041s/ -s 3 2 1 -H |
+            cut -f 2- | sed s/-32768/-2048/ |
+            gzip -9 -n > tests/target-output/record-multi-fixed-d.gz
+        """
+        record = wfdb.rdrecord(
+            "sample-data/multi-segment/041s/041s",
+            channels=[3, 2, 1],
+            physical=False,
+            smooth_frames=False,
+        )
+
+        # Convert expanded to uniform array (high-resolution)
+        sig = np.zeros((record.sig_len * 4, record.n_sig), dtype=int)
+        for i, s in enumerate(record.e_d_signal):
+            sig[:, i] = np.repeat(s, len(sig[:, i]) // len(s))
+
+        sig_target = np.genfromtxt(
+            "tests/target-output/record-multi-fixed-d.gz"
+        )
+
+        record_named = wfdb.rdrecord(
+            "sample-data/multi-segment/041s/041s",
+            channel_names=["ABP", "V", "I"],
+            physical=False,
+            smooth_frames=False,
+        )
+
+        np.testing.assert_array_equal(sig, sig_target)
+        assert record.__eq__(record_named)
+
     def test_multi_variable_a(self):
         """
         Multi-segment, variable layout, selected duration, samples read