pytest: test parsefeerate explicitly.

Since we're messing with feerates, it's good to test this directly upfront.

Also, fix documentation!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

doc/lightning-feerates.7.md

@@ -48,7 +48,7 @@ RETURN VALUE
 On success, an object is returned, containing:
 
 - **perkb** (object, optional): If *style* parameter was perkb:
-  - **min\_acceptable** (u32): The smallest feerate that you can use, usually the minimum relayed feerate of the backend
+  - **min\_acceptable** (u32): The smallest feerate that we allow peers to specify: half the 100-block estimate
   - **max\_acceptable** (u32): The largest feerate we will accept from remote negotiations.  If a peer attempts to set the feerate higher than this we will unilaterally close the channel (or simply forget it if it's not open yet).
   - **opening** (u32, optional): Default feerate for lightning-fundchannel(7) and lightning-withdraw(7)
   - **mutual\_close** (u32, optional): Feerate to aim for in cooperative shutdown.  Note that since mutual close is a **negotiation**, the actual feerate used in mutual close will be somewhere between this and the corresponding mutual close feerate of the peer.
@@ -121,4 +121,4 @@ RESOURCES
 
 Main web site: <https://github.com/ElementsProject/lightning>
 
-[comment]: # ( SHA256STAMP:a34af89895413ee57defa1df715d9e50d34a49196972a81b31a4666b4fc05a10)
+[comment]: # ( SHA256STAMP:773e4e66cb3654b7c3aafe54c33d433c52ff89f7a5a8be0a71a93da21a6b7eaa)

doc/schemas/feerates.schema.json

@@ -19,7 +19,7 @@
       "properties": {
         "min_acceptable": {
           "type": "u32",
-          "description": "The smallest feerate that you can use, usually the minimum relayed feerate of the backend"
+          "description": "The smallest feerate that we allow peers to specify: half the 100-block estimate"
         },
         "max_acceptable": {
           "type": "u32",

tests/test_misc.py

@@ -3214,6 +3214,39 @@ def test_hsm_capabilities(node_factory):
     assert l1.daemon.is_in_log(r"hsmd: capability \+WIRE_HSMD_CHECK_PUBKEY")
 
 
+def test_feerate_arg(node_factory):
+    """Make sure our variants of feerate argument work!"""
+    l1 = node_factory.get_node()
+
+    # These are the get_node() defaults
+    by_blocks = {2: 15000,
+                 6: 11000,
+                 12: 7500,
+                 100: 3750}
+
+    # Literal values:
+    fees = {"9999perkw": 9999,
+            "10000perkb": 10000 // 4,
+            10000: 10000 // 4}
+
+    fees["urgent"] = by_blocks[6]
+    fees["normal"] = by_blocks[12]
+    fees["slow"] = by_blocks[100] // 2
+
+    fees["opening"] = by_blocks[12]
+    fees["mutual_close"] = by_blocks[100]
+    fees["penalty"] = by_blocks[12]
+    fees["unilateral_close"] = by_blocks[6]
+    fees["delayed_to_us"] = by_blocks[12]
+    fees["htlc_resolution"] = by_blocks[6]
+    fees["min_acceptable"] = by_blocks[100] // 2
+    fees["max_acceptable"] = by_blocks[2] * 10
+
+    for fee, expect in fees.items():
+        # Put arg in assertion, so it gets printed on failure!
+        assert (l1.rpc.parsefeerate(fee), fee) == ({'perkw': expect}, fee)
+
+
 @pytest.mark.skip(reason="Fails by intention for creating test gossip stores")
 def test_create_gossip_mesh(node_factory, bitcoind):
     """