Merge #417: Add support for writing integration tests that fail

ab79593 Use DescError instead of miniscript::Error (kanishk779)
b446ced Add support for writing integration tests that fail (kanishk779)

Pull request description:

  - Earlier we did not have the ability to write integration tests that fail.
  - The default behaviour was to panic and stop the execution of the program.
  - But in addition to verifying that the code works in the correct cases, we must also ensure that it should generate an appropriate error in incorrect cases.
  - Some functions are modified to return Result<T, E> to support this feature.
  - Four failing tests have also been added (tests 10-13) to demonstrate this.

ACKs for top commit:
  sanket1729:
    ACK ab79593

Tree-SHA512: 2f0800194c06325cd32fc81988f88989d412c4d0164d8d3f2105068a16db22a3e25fcdefe9f1c7736739faf765fb1e8adc850f9c524e7dec7c89af4dcca22e47

Author: sanket1729

tests/setup/test_util.rs

@@ -25,10 +25,9 @@ use bitcoin::hashes::{hash160, ripemd160, sha256, sha256d, Hash};
 use bitcoin::secp256k1;
 use miniscript::descriptor::{SinglePub, SinglePubKey};
 use miniscript::{
-    Descriptor, DescriptorPublicKey, Miniscript, ScriptContext, TranslatePk, Translator,
+    Descriptor, DescriptorPublicKey, Error, Miniscript, ScriptContext, TranslatePk, Translator,
 };
 use rand::RngCore;
-
 #[derive(Clone, Debug)]
 pub struct PubData {
     pub pks: Vec<bitcoin::PublicKey>,
@@ -248,13 +247,15 @@ impl<'a> Translator<String, DescriptorPublicKey, ()> for StrTranslatorLoose<'a>
 
 #[allow(dead_code)]
 // https://github.com/rust-lang/rust/issues/46379. The code is pub fn and integration test, but still shows warnings
-pub fn parse_test_desc(desc: &str, pubdata: &PubData) -> Descriptor<DescriptorPublicKey> {
+pub fn parse_test_desc(
+    desc: &str,
+    pubdata: &PubData,
+) -> Result<Descriptor<DescriptorPublicKey>, Error> {
     let desc = subs_hash_frag(desc, pubdata);
-    let desc =
-        Descriptor::<String>::from_str(&desc).expect("only parsing valid and sane descriptors");
+    let desc = Descriptor::<String>::from_str(&desc)?;
     let mut translator = StrDescPubKeyTranslator(0, pubdata);
     let desc: Result<_, ()> = desc.translate_pk(&mut translator);
-    desc.expect("Translate must succeed")
+    Ok(desc.expect("Translate must succeed"))
 }
 
 // substitute hash fragments in the string as the per rules