Add tests for `test_read_snapshot`

In particular for several SHPC.

Overlap/Tests/short_tests.json

@@ -569,5 +569,51 @@
 	    ]
         ],
 	"input": "&main_nml ishape = 330 /\n"
+    },
+    {
+        "input": "&main_nml /\n",
+        "title": "Read_snapshot_15",
+	"description": "Read a snapshot from an SHPC with a sufficient number of dates: 15. $tests_old_dir/Extraction_eddies_region_4/SHPC_anti used by the test Read_snapshot has only 2 dates.",
+        "commands": [
+            [
+                "mkdir",
+                "SHPC"
+            ],
+            [
+                "$build_dir/Overlap/Tests/test_read_snapshot",
+                "$PWD/Inst_eddies_10_anti"
+            ]
+        ]
+    },
+    {
+        "input": "&main_nml k = 20461/\n",
+        "title": "Read_snapshot_middle",
+	"description": "Like Read_snapshot_15, but we read a date other than the first date.",
+        "commands": [
+            [
+                "mkdir",
+                "SHPC"
+            ],
+            [
+                "$build_dir/Overlap/Tests/test_read_snapshot",
+                "$PWD/Inst_eddies_10_anti"
+            ]
+        ]
+    },
+    {
+        "input": "&main_nml k = 20461/\n",
+        "title": "Read_snapshot_several",
+	"description": "Like Read_snapshot_middle, but we read from several SHPC. The 3 SHPC are just the result from splitting Inst_eddies_10_anti.",
+        "commands": [
+            [
+                "mkdir",
+                "SHPC"
+            ],
+            [
+                "$build_dir/Overlap/Tests/test_read_snapshot",
+                "$PWD/Inst_eddies_10_anti_1", "$PWD/Inst_eddies_10_anti_2",
+		"$PWD/Inst_eddies_10_anti_3"
+            ]
+        ]
     }
 ]