diff --git a/Cargo.toml b/Cargo.toml
index 5f02f1ca..53dd08b6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -40,8 +40,10 @@ sophia_turtle = { version = "0.8.0", path = "./turtle" }
 sophia_xml = { version = "0.8.0", path = "./xml" }
 
 criterion = "0.5"
+env_logger = "0.11.3"
 futures-util = "0.3.28"
 lazy_static = "1.4.0"
+log = "0.4.21"
 mownstr = "0.2.1"
 oxiri = "0.2.2"
 regex = "1.6.0"
diff --git a/c14n/Cargo.toml b/c14n/Cargo.toml
index 00e42315..9f2cf76d 100644
--- a/c14n/Cargo.toml
+++ b/c14n/Cargo.toml
@@ -13,7 +13,11 @@ keywords.workspace = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+log.workspace = true
 sha2 = "0.10.7"
 sophia_api.workspace = true
 sophia_iri.workspace = true
-thiserror.workspace = true
\ No newline at end of file
+thiserror.workspace = true
+
+[dev-dependencies]
+env_logger.workspace = true
diff --git a/c14n/src/_permutations.rs b/c14n/src/_permutations.rs
index 842dc4f3..e1a459af 100644
--- a/c14n/src/_permutations.rs
+++ b/c14n/src/_permutations.rs
@@ -37,6 +37,8 @@ mod test {
 
     #[test]
     fn check_empty() {
+        crate::test_setup();
+
         let mut a = [];
         let mut got = HashSet::<Vec<i32>>::new();
         for_each_permutation_of(&mut a, |a| {
@@ -49,6 +51,8 @@ mod test {
 
     #[test]
     fn check_1() {
+        crate::test_setup();
+
         let mut a = [1];
         let exp = [vec![1]].into_iter().collect::<HashSet<_>>();
         let mut got = HashSet::<Vec<i32>>::new();
@@ -62,6 +66,8 @@ mod test {
 
     #[test]
     fn check_12() {
+        crate::test_setup();
+
         let mut a = [1, 2];
         let exp = [vec![1, 2], vec![2, 1]].into_iter().collect::<HashSet<_>>();
         let mut got = HashSet::<Vec<i32>>::new();
@@ -75,6 +81,8 @@ mod test {
 
     #[test]
     fn check_123() {
+        crate::test_setup();
+
         let mut a = [1, 2, 3];
         let exp = [
             vec![1, 2, 3],
@@ -97,6 +105,8 @@ mod test {
 
     #[test]
     fn check_1234() {
+        crate::test_setup();
+
         let mut a = [1, 2, 3, 4];
         let exp = [
             vec![1, 2, 3, 4],
@@ -137,6 +147,8 @@ mod test {
 
     #[test]
     fn check_12345() {
+        crate::test_setup();
+
         let mut a = [1, 2, 3, 4, 5];
         let mut got = HashSet::<Vec<i32>>::new();
         for_each_permutation_of(&mut a, |a| {
@@ -149,6 +161,8 @@ mod test {
 
     #[test]
     fn check_err() {
+        crate::test_setup();
+
         let mut a = [1, 2, 3, 4];
         let exp = [
             vec![1, 2, 3, 4],
diff --git a/c14n/src/lib.rs b/c14n/src/lib.rs
index 94a9285a..acef4c25 100644
--- a/c14n/src/lib.rs
+++ b/c14n/src/lib.rs
@@ -40,3 +40,13 @@ pub enum C14nError<E: std::error::Error> {
     #[error("Unsupported feature: {0}")]
     Unsupported(String),
 }
+
+#[cfg(test)]
+fn test_setup() {
+    TEST_SETUP.call_once(|| {
+        env_logger::init();
+    });
+}
+
+#[cfg(test)]
+static TEST_SETUP: std::sync::Once = std::sync::Once::new();
diff --git a/c14n/src/rdfc10.rs b/c14n/src/rdfc10.rs
index afa399a6..2195608b 100644
--- a/c14n/src/rdfc10.rs
+++ b/c14n/src/rdfc10.rs
@@ -398,7 +398,7 @@ impl<'a, H: HashFunction, T: Term> C14nState<'a, H, T> {
             ret_issuer.unwrap_or_else(|| issuer.clone()),
         );
         debug_assert!({
-            eprintln!(
+            log::trace!(
                 "hash-n-degree({}, {})\n-> {}",
                 identifier,
                 depth,
@@ -470,7 +470,7 @@ fn hash_first_degree_quads<H: HashFunction, Q: Quad>(bnid: &str, quads: &[&Q]) -
     }
     let ret = hasher.finalize();
     debug_assert!({
-        eprintln!("hash-first-degree({})\n-> {}", bnid, hex(&ret));
+        log::trace!("hash-first-degree({})\n-> {}", bnid, hex(&ret));
         true
     });
     ret
@@ -520,6 +520,8 @@ mod test {
 
     #[test]
     fn example2() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "<http://example.com/#p> <http://example.com/#q> _:e0 .",
             "<http://example.com/#p> <http://example.com/#r> _:e1 .",
@@ -538,6 +540,8 @@ _:c14n1 <http://example.com/#t> <http://example.com/#u> .
 
     #[test]
     fn example3() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "<http://example.com/#p> <http://example.com/#q> _:e0 .",
             "<http://example.com/#p> <http://example.com/#q> _:e1 .",
@@ -558,6 +562,8 @@ _:c14n3 <http://example.com/#p> _:c14n0 .
 
     #[test]
     fn cycle5() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "_:e0 <http://example.com/#p> _:e1 .",
             "_:e1 <http://example.com/#p> _:e2 .",
@@ -578,6 +584,8 @@ _:c14n4 <http://example.com/#p> _:c14n3 .
 
     #[test]
     fn cycle5_toxic() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "_:e0 <http://example.com/#p> _:e1 .",
             "_:e1 <http://example.com/#p> _:e2 .",
@@ -598,6 +606,8 @@ _:c14n4 <http://example.com/#p> _:c14n3 .
 
     #[test]
     fn clique5() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "_:e0 <http://example.com/#p> _:e1 .",
             "_:e0 <http://example.com/#p> _:e2 .",
@@ -648,6 +658,8 @@ _:c14n4 <http://example.com/#p> _:c14n3 .
 
     #[test]
     fn clique5_toxic() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "_:e0 <http://example.com/#p> _:e1 .",
             "_:e0 <http://example.com/#p> _:e2 .",
@@ -679,6 +691,8 @@ _:c14n4 <http://example.com/#p> _:c14n3 .
 
     #[test]
     fn cycle2plus3() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "_:e0 <http://example.com/#p> _:e1 .",
             "_:e1 <http://example.com/#p> _:e0 .",
@@ -699,6 +713,8 @@ _:c14n4 <http://example.com/#p> _:c14n3 .
 
     #[test]
     fn tricky_order() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "<tag:a> <tag:p> _:a .",
             "<tag:a> <tag:p> <tag:a> .",
@@ -780,6 +796,8 @@ _:c14n4 <http://example.com/#p> _:c14n3 .
 
     #[test]
     fn example2_sha384() {
+        crate::test_setup();
+
         let dataset = ez_quads(&[
             "<http://example.com/#p> <http://example.com/#q> _:e0 .",
             "<http://example.com/#p> <http://example.com/#r> _:e1 .",