diff --git a/milli/src/search/criteria/mod.rs b/milli/src/search/criteria/mod.rs
index 3673aef78..77d92f6ea 100644
--- a/milli/src/search/criteria/mod.rs
+++ b/milli/src/search/criteria/mod.rs
@@ -14,6 +14,7 @@ pub trait Criterion {
 }
 
 /// The result of a call to the parent criterion.
+#[derive(Debug, Clone, PartialEq)]
 pub struct CriterionResult {
     /// The query tree that must be used by the children criterion to fetch candidates.
     pub query_tree: Option<Operation>,
@@ -188,3 +189,139 @@ fn query_pair_proximity_docids(ctx: &dyn Context, left: &Query, right: &Query, p
         },
     }
 }
+
+#[cfg(test)]
+pub mod test {
+    use maplit::hashmap;
+    use rand::{Rng, SeedableRng, rngs::StdRng};
+
+    use super::*;
+    use std::collections::HashMap;
+
+    fn s(s: &str) -> String { s.to_string() }
+    pub struct TestContext<'t> {
+        words_fst: fst::Set<Cow<'t, [u8]>>,
+        word_docids: HashMap<String, RoaringBitmap>,
+        word_prefix_docids: HashMap<String, RoaringBitmap>,
+        word_pair_proximity_docids: HashMap<(String, String, i32), RoaringBitmap>,
+        word_prefix_pair_proximity_docids: HashMap<(String, String, i32), RoaringBitmap>,
+    }
+
+    impl<'a> Context for TestContext<'a> {
+        fn word_docids(&self, word: &str) -> heed::Result<Option<RoaringBitmap>> {
+            Ok(self.word_docids.get(&word.to_string()).cloned())
+        }
+
+        fn word_prefix_docids(&self, word: &str) -> heed::Result<Option<RoaringBitmap>> {
+            Ok(self.word_prefix_docids.get(&word.to_string()).cloned())
+        }
+
+        fn word_pair_proximity_docids(&self, left: &str, right: &str, proximity: u8) -> heed::Result<Option<RoaringBitmap>> {
+            let key = (left.to_string(), right.to_string(), proximity.into());
+            Ok(self.word_pair_proximity_docids.get(&key).cloned())
+        }
+
+        fn word_prefix_pair_proximity_docids(&self, left: &str, right: &str, proximity: u8) -> heed::Result<Option<RoaringBitmap>> {
+            let key = (left.to_string(), right.to_string(), proximity.into());
+            Ok(self.word_prefix_pair_proximity_docids.get(&key).cloned())
+        }
+
+        fn words_fst<'t>(&self) -> &'t fst::Set<Cow<[u8]>> {
+            &self.words_fst
+        }
+
+        fn in_prefix_cache(&self, word: &str) -> bool {
+            self.word_prefix_docids.contains_key(&word.to_string())
+        }
+    }
+
+    impl<'a> Default for TestContext<'a> {
+        fn default() -> TestContext<'a> {
+            let mut rng = StdRng::seed_from_u64(102);
+            let rng = &mut rng;
+
+            fn random_postings<R: Rng>(rng: &mut R, len: usize) -> RoaringBitmap {
+                let mut values = Vec::<u32>::with_capacity(len);
+                while values.len() != len {
+                    values.push(rng.gen());
+                }
+                values.sort_unstable();
+
+                RoaringBitmap::from_sorted_iter(values.into_iter())
+            }
+
+            let word_docids = hashmap!{
+                s("hello")      => random_postings(rng,   1500),
+                s("hi")         => random_postings(rng,   4000),
+                s("word")       => random_postings(rng,   2500),
+                s("split")      => random_postings(rng,    400),
+                s("ngrams")     => random_postings(rng,   1400),
+                s("world")      => random_postings(rng, 15_000),
+                s("earth")      => random_postings(rng,   8000),
+                s("2021")       => random_postings(rng,    100),
+                s("2020")       => random_postings(rng,    500),
+                s("is")         => random_postings(rng, 50_000),
+                s("this")       => random_postings(rng, 50_000),
+                s("good")       => random_postings(rng,   1250),
+                s("morning")    => random_postings(rng,    125),
+            };
+
+            let word_prefix_docids = hashmap!{
+                s("h")   => &word_docids[&s("hello")] | &word_docids[&s("hi")],
+                s("wor") => &word_docids[&s("word")]  | &word_docids[&s("world")],
+                s("20")  => &word_docids[&s("2020")]  | &word_docids[&s("2021")],
+            };
+
+            let hello_world = &word_docids[&s("hello")] & &word_docids[&s("world")];
+            let hello_world_split = (hello_world.len() / 2) as usize;
+            let hello_world_1 = hello_world.iter().take(hello_world_split).collect();
+            let hello_world_2 = hello_world.iter().skip(hello_world_split).collect();
+
+            let hello_word = &word_docids[&s("hello")] & &word_docids[&s("word")];
+            let hello_word_split = (hello_word.len() / 2) as usize;
+            let hello_word_4 = hello_word.iter().take(hello_word_split).collect();
+            let hello_word_6 = hello_word.iter().skip(hello_word_split).take(hello_word_split/2).collect();
+            let hello_word_7 = hello_word.iter().skip(hello_word_split + hello_word_split/2).collect();
+            let word_pair_proximity_docids = hashmap!{
+                (s("good"), s("morning"), 1)   => &word_docids[&s("good")] & &word_docids[&s("morning")],
+                (s("hello"), s("world"), 1)   => hello_world_1,
+                (s("hello"), s("world"), 4)   => hello_world_2,
+                (s("this"), s("is"), 1)   => &word_docids[&s("this")] & &word_docids[&s("is")],
+                (s("is"), s("2021"), 1)   => &word_docids[&s("this")] & &word_docids[&s("is")] & &word_docids[&s("2021")],
+                (s("is"), s("2020"), 1)   => &word_docids[&s("this")] & &word_docids[&s("is")] & (&word_docids[&s("2020")] - &word_docids[&s("2021")]),
+                (s("this"), s("2021"), 2)   => &word_docids[&s("this")] & &word_docids[&s("is")] & &word_docids[&s("2021")],
+                (s("this"), s("2020"), 2)   => &word_docids[&s("this")] & &word_docids[&s("is")] & (&word_docids[&s("2020")] - &word_docids[&s("2021")]),
+                (s("word"), s("split"), 1)   => &word_docids[&s("word")] & &word_docids[&s("split")],
+                (s("world"), s("split"), 1)   => (&word_docids[&s("world")] & &word_docids[&s("split")]) - &word_docids[&s("word")],
+                (s("hello"), s("word"), 4) => hello_word_4,
+                (s("hello"), s("word"), 6) => hello_word_6,
+                (s("hello"), s("word"), 7) => hello_word_7,
+                (s("split"), s("ngrams"), 3)   => (&word_docids[&s("split")] & &word_docids[&s("ngrams")]) - &word_docids[&s("word")],
+                (s("split"), s("ngrams"), 5)   => &word_docids[&s("split")] & &word_docids[&s("ngrams")] & &word_docids[&s("word")],
+                (s("this"), s("ngrams"), 1)   => (&word_docids[&s("split")] & &word_docids[&s("this")] & &word_docids[&s("ngrams")] ) - &word_docids[&s("word")],
+                (s("this"), s("ngrams"), 2)   => &word_docids[&s("split")] & &word_docids[&s("this")] & &word_docids[&s("ngrams")] & &word_docids[&s("word")],
+            };
+
+            let word_prefix_pair_proximity_docids = hashmap!{
+                (s("hello"), s("wor"), 1) => word_pair_proximity_docids.get(&(s("hello"), s("world"), 1)).unwrap().clone(),
+                (s("hello"), s("wor"), 4) => word_pair_proximity_docids.get(&(s("hello"), s("world"), 4)).unwrap() | word_pair_proximity_docids.get(&(s("hello"), s("word"), 4)).unwrap(),
+                (s("hello"), s("wor"), 6) => word_pair_proximity_docids.get(&(s("hello"), s("word"), 6)).unwrap().clone(),
+                (s("hello"), s("wor"), 7) => word_pair_proximity_docids.get(&(s("hello"), s("word"), 7)).unwrap().clone(),
+                (s("is"), s("20"), 1) => word_pair_proximity_docids.get(&(s("is"), s("2020"), 1)).unwrap() | word_pair_proximity_docids.get(&(s("is"), s("2021"), 1)).unwrap(),
+                (s("this"), s("20"), 2) => word_pair_proximity_docids.get(&(s("this"), s("2020"), 2)).unwrap() | word_pair_proximity_docids.get(&(s("this"), s("2021"), 2)).unwrap(),
+            };
+
+            let mut keys = word_docids.keys().collect::<Vec<_>>();
+            keys.sort_unstable();
+            let words_fst = fst::Set::from_iter(keys).unwrap().map_data(|v| Cow::Owned(v)).unwrap();
+
+            TestContext {
+                words_fst,
+                word_docids,
+                word_prefix_docids,
+                word_pair_proximity_docids,
+                word_prefix_pair_proximity_docids,
+            }
+        }
+    }
+}
diff --git a/milli/src/search/criteria/typo.rs b/milli/src/search/criteria/typo.rs
index 75f3f5666..d9a5f8aa6 100644
--- a/milli/src/search/criteria/typo.rs
+++ b/milli/src/search/criteria/typo.rs
@@ -328,3 +328,153 @@ fn resolve_candidates<'t>(
 
     resolve_operation(ctx, query_tree, number_typos, cache)
 }
+
+#[cfg(test)]
+mod test {
+
+    use super::*;
+    use super::super::test::TestContext;
+
+    #[test]
+    fn initial_placeholder_no_facets() {
+        let context = TestContext::default();
+        let query_tree = None;
+        let facet_candidates = None;
+
+        let mut criteria = Typo::initial(&context, query_tree, facet_candidates).unwrap();
+
+        assert!(criteria.next().unwrap().is_none());
+    }
+
+    #[test]
+    fn initial_query_tree_no_facets() {
+        let context = TestContext::default();
+        let query_tree = Operation::Or(false, vec![
+            Operation::And(vec![
+                Operation::Query(Query { prefix: false, kind: QueryKind::exact("split".to_string()) }),
+                Operation::Query(Query { prefix: false, kind: QueryKind::exact("this".to_string()) }),
+                Operation::Query(Query { prefix: false, kind: QueryKind::tolerant(1, "world".to_string()) }),
+            ])
+        ]);
+
+        let facet_candidates = None;
+
+        let mut criteria = Typo::initial(&context, Some(query_tree), facet_candidates).unwrap();
+
+        let candidates_1 = context.word_docids("split").unwrap().unwrap()
+            & context.word_docids("this").unwrap().unwrap()
+            & context.word_docids("world").unwrap().unwrap();
+        let expected_1 = CriterionResult {
+            query_tree: Some(Operation::Or(false, vec![
+                Operation::And(vec![
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("split".to_string()) }),
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("this".to_string()) }),
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("world".to_string()) }),
+                ]),
+            ])),
+            candidates: candidates_1.clone(),
+            bucket_candidates: Some(candidates_1),
+        };
+
+        assert_eq!(criteria.next().unwrap(), Some(expected_1));
+
+        let candidates_2 = (
+                context.word_docids("split").unwrap().unwrap()
+                & context.word_docids("this").unwrap().unwrap()
+                & context.word_docids("word").unwrap().unwrap()
+            ) - context.word_docids("world").unwrap().unwrap();
+        let expected_2 = CriterionResult {
+            query_tree: Some(Operation::Or(false, vec![
+                Operation::And(vec![
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("split".to_string()) }),
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("this".to_string()) }),
+                    Operation::Or(false, vec![
+                        Operation::Query(Query { prefix: false, kind: QueryKind::exact_with_typo(1, "word".to_string()) }),
+                        Operation::Query(Query { prefix: false, kind: QueryKind::exact("world".to_string()) }),
+                    ]),
+                ]),
+            ])),
+            candidates: candidates_2.clone(),
+            bucket_candidates: Some(candidates_2),
+        };
+
+        assert_eq!(criteria.next().unwrap(), Some(expected_2));
+    }
+
+    #[test]
+    fn initial_placeholder_with_facets() {
+        let context = TestContext::default();
+        let query_tree = None;
+        let facet_candidates = context.word_docids("earth").unwrap();
+
+        let mut criteria = Typo::initial(&context, query_tree, facet_candidates.clone()).unwrap();
+
+        let expected = CriterionResult {
+            query_tree: None,
+            candidates: facet_candidates.clone().unwrap(),
+            bucket_candidates: facet_candidates,
+        };
+
+        // first iteration, returns the facet candidates
+        assert_eq!(criteria.next().unwrap(), Some(expected));
+
+        // second iteration, returns None because there is no more things to do
+        assert!(criteria.next().unwrap().is_none());
+    }
+
+    #[test]
+    fn initial_query_tree_with_facets() {
+        let context = TestContext::default();
+        let query_tree = Operation::Or(false, vec![
+            Operation::And(vec![
+                Operation::Query(Query { prefix: false, kind: QueryKind::exact("split".to_string()) }),
+                Operation::Query(Query { prefix: false, kind: QueryKind::exact("this".to_string()) }),
+                Operation::Query(Query { prefix: false, kind: QueryKind::tolerant(1, "world".to_string()) }),
+            ])
+        ]);
+
+        let facet_candidates = context.word_docids("earth").unwrap().unwrap();
+
+        let mut criteria = Typo::initial(&context, Some(query_tree), Some(facet_candidates.clone())).unwrap();
+
+        let candidates_1 = context.word_docids("split").unwrap().unwrap()
+            & context.word_docids("this").unwrap().unwrap()
+            & context.word_docids("world").unwrap().unwrap();
+        let expected_1 = CriterionResult {
+            query_tree: Some(Operation::Or(false, vec![
+                Operation::And(vec![
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("split".to_string()) }),
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("this".to_string()) }),
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("world".to_string()) }),
+                ]),
+            ])),
+            candidates: &candidates_1 & &facet_candidates,
+            bucket_candidates: Some(candidates_1 & &facet_candidates),
+        };
+
+        assert_eq!(criteria.next().unwrap(), Some(expected_1));
+
+        let candidates_2 = (
+                context.word_docids("split").unwrap().unwrap()
+                & context.word_docids("this").unwrap().unwrap()
+                & context.word_docids("word").unwrap().unwrap()
+            ) - context.word_docids("world").unwrap().unwrap();
+        let expected_2 = CriterionResult {
+            query_tree: Some(Operation::Or(false, vec![
+                Operation::And(vec![
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("split".to_string()) }),
+                    Operation::Query(Query { prefix: false, kind: QueryKind::exact("this".to_string()) }),
+                    Operation::Or(false, vec![
+                        Operation::Query(Query { prefix: false, kind: QueryKind::exact_with_typo(1, "word".to_string()) }),
+                        Operation::Query(Query { prefix: false, kind: QueryKind::exact("world".to_string()) }),
+                    ]),
+                ]),
+            ])),
+            candidates: &candidates_2 & &facet_candidates,
+            bucket_candidates: Some(candidates_2 & &facet_candidates),
+        };
+
+        assert_eq!(criteria.next().unwrap(), Some(expected_2));
+    }
+
+}
diff --git a/milli/src/search/query_tree.rs b/milli/src/search/query_tree.rs
index 02f6dc0c8..715a4864e 100644
--- a/milli/src/search/query_tree.rs
+++ b/milli/src/search/query_tree.rs
@@ -94,11 +94,15 @@ pub enum QueryKind {
 }
 
 impl QueryKind {
-    fn exact(word: String) -> Self {
+    pub fn exact(word: String) -> Self {
         QueryKind::Exact { original_typo: 0, word }
     }
 
-    fn tolerant(typo: u8, word: String) -> Self {
+    pub fn exact_with_typo(original_typo: u8, word: String) -> Self {
+        QueryKind::Exact { original_typo, word }
+    }
+
+    pub fn tolerant(typo: u8, word: String) -> Self {
         QueryKind::Tolerant { typo, word }
     }