diff --git a/test/clojure/string_test/blank_qmark.cljc b/test/clojure/string_test/blank_qmark.cljc
index 3256b6b7..aeaa274f 100644
--- a/test/clojure/string_test/blank_qmark.cljc
+++ b/test/clojure/string_test/blank_qmark.cljc
@@ -22,7 +22,10 @@
        :default (is (p/thrown? (str/blank? (keyword "")))))
     #?(:cljs (is (false? (str/blank? 1)))
        :default (is (p/thrown? (str/blank? 1))))
-    #?(:lpy (is (true? (str/blank? \space)))
+    ;; Phel reads `\space` as the single-space string " ", so `blank?` returns
+    ;; true (it is whitespace) rather than throwing on a character type.
+    #?(:phel (is (true? (str/blank? \space)))
+       :lpy (is (true? (str/blank? \space)))
        :cljs (do (is (true? (str/blank? \space)))
                  (is (false? (str/blank? \a))))
        :default (is (p/thrown? (str/blank? \space))))
diff --git a/test/clojure/string_test/capitalize.cljc b/test/clojure/string_test/capitalize.cljc
index 2c2d8cc9..af5ba402 100644
--- a/test/clojure/string_test/capitalize.cljc
+++ b/test/clojure/string_test/capitalize.cljc
@@ -6,7 +6,14 @@
 (when-var-exists str/capitalize
   (deftest test-capitalize
     (is (p/thrown? (str/capitalize nil)))
-    #?(:cljr (do (is (p/thrown? (str/capitalize 1)))
+    ;; Phel's string functions are strict: a non-string argument throws
+    ;; rather than being coerced via `str`/`toString` (the JVM `:default`
+    ;; behaviour). Documented divergence; matches the :cljs/:lpy/:cljr stance.
+    #?(:phel (do (is (p/thrown? (str/capitalize 1)))
+                 (is (p/thrown? (str/capitalize 'Asdf)))
+                 (is (p/thrown? (str/capitalize 'asDf/aSdf)))
+                 (is (p/thrown? (str/capitalize :asDf/aSdf))))
+       :cljr (do (is (p/thrown? (str/capitalize 1)))
                  (is (p/thrown? (str/capitalize 'Asdf)))
                  (is (p/thrown? (str/capitalize 'asDf/aSdf)))
                  (is (p/thrown? (str/capitalize :asDf/aSdf))))
diff --git a/test/clojure/string_test/ends_with_qmark.cljc b/test/clojure/string_test/ends_with_qmark.cljc
index 3537c03a..2eb07d5d 100644
--- a/test/clojure/string_test/ends_with_qmark.cljc
+++ b/test/clojure/string_test/ends_with_qmark.cljc
@@ -19,7 +19,15 @@
     #?(:cljs (is (false? (str/ends-with? "ab" 'b)))
        :default (is (p/thrown? (str/ends-with? "ab" 'b))))
 
-   #?@(:cljr
+   ;; Phel's string functions are strict: a non-string argument throws
+   ;; rather than being coerced via `str`/`toString` (the JVM `:default`
+   ;; behaviour). Documented divergence; matches the :cljs/:lpy/:cljr stance.
+   #?@(:phel
+       [(is (p/thrown? (str/ends-with? 'ab "b")))
+        (is (p/thrown? (str/ends-with? 'ab "a")))
+        (is (p/thrown? (str/ends-with? :ab "b")))
+        (is (p/thrown? (str/ends-with? :ab "b")))]
+       :cljr
        [(is (p/thrown? (str/ends-with? 'ab "b")))
         (is (p/thrown? (str/ends-with? 'ab "a")))
         (is (p/thrown? (str/ends-with? :ab "b")))
diff --git a/test/clojure/string_test/lower_case.cljc b/test/clojure/string_test/lower_case.cljc
index 39e6124f..17ac6036 100644
--- a/test/clojure/string_test/lower_case.cljc
+++ b/test/clojure/string_test/lower_case.cljc
@@ -13,7 +13,17 @@
     (let [s "ASDF"]
       (is (= "asdf" (str/lower-case "ASDF")))
       (is (= "ASDF" s) "original string mutated"))
-    #?(:cljr
+    ;; Phel's string functions are strict: a non-string argument throws
+    ;; rather than being coerced via `str`/`toString` (the JVM `:default`
+    ;; behaviour). Documented divergence; matches the :cljs/:lpy/:cljr stance.
+    #?(:phel
+       (are [v] (p/thrown? (str/lower-case v))
+         :ASDF
+         :ASDF/ASDF
+         'ASDF
+         'ASDF/ASDF)
+
+       :cljr
        (are [v] (p/thrown? (str/lower-case v))
          :ASDF
          :ASDF/ASDF
diff --git a/test/clojure/string_test/starts_with_qmark.cljc b/test/clojure/string_test/starts_with_qmark.cljc
index 6cf23b10..b46609a2 100644
--- a/test/clojure/string_test/starts_with_qmark.cljc
+++ b/test/clojure/string_test/starts_with_qmark.cljc
@@ -28,7 +28,15 @@
     (is (false? (str/starts-with? "a-test" "-")))
     (is (false? (str/starts-with? "a-test" "t")))
 
-    #?@(:cljr
+    ;; Phel's string functions are strict: a non-string argument throws
+    ;; rather than being coerced via `str`/`toString` (the JVM `:default`
+    ;; behaviour). Documented divergence; matches the :cljs/:lpy/:cljr stance.
+    #?@(:phel
+        [(is (p/thrown? (str/starts-with? 'ab ":a")))
+         (is (p/thrown? (str/starts-with? :ab ":a")))
+         (is (p/thrown? (str/starts-with? 'a/b ":a")))
+         (is (p/thrown? (str/starts-with? :a/b ":a")))]
+        :cljr
         [(is (p/thrown? (str/starts-with? 'ab ":a")))
          (is (p/thrown? (str/starts-with? :ab ":a")))
          (is (p/thrown? (str/starts-with? 'a/b ":a")))
diff --git a/test/clojure/string_test/upper_case.cljc b/test/clojure/string_test/upper_case.cljc
index 738f43a3..6dc01723 100644
--- a/test/clojure/string_test/upper_case.cljc
+++ b/test/clojure/string_test/upper_case.cljc
@@ -13,7 +13,17 @@
     (let [s "asdf"]
       (is (= "ASDF" (str/upper-case "asdf")))
       (is (= "asdf" s) "original string mutated"))
-    #?(:cljr
+    ;; Phel's string functions are strict: a non-string argument throws
+    ;; rather than being coerced via `str`/`toString` (the JVM `:default`
+    ;; behaviour). Documented divergence; matches the :cljs/:lpy/:cljr stance.
+    #?(:phel
+       (are [v] (p/thrown? (str/upper-case v))
+         :asdf
+         :asdf/asdf
+         'asdf
+         'asdf/asdf)
+
+       :cljr
        (are [v] (p/thrown? (str/upper-case v))
          :asdf
          :asdf/asdf