diff --git a/src/handlers/get_value.rs b/src/handlers/get_value.rs
index 3597ce4..7dbe24c 100644
--- a/src/handlers/get_value.rs
+++ b/src/handlers/get_value.rs
@@ -12,7 +12,7 @@ pub fn get_value(options: &Options) -> bool {
     let env_object = options.env_object.as_ref().unwrap();
     let mut all_found = true;
 
-    let keys: Vec<String> = if options.target_keys.is_empty() {
+    let keys: Vec<String> = if options.return_all_keys {
         env_object.keys().cloned().collect()
     } else {
         options.target_keys.clone()
diff --git a/tests/debug.rs b/tests/debug.rs
new file mode 100644
index 0000000..492fcf6
--- /dev/null
+++ b/tests/debug.rs
@@ -0,0 +1,100 @@
+use assert_cmd::Command;
+use predicates::prelude::*;
+use std::path::Path;
+
+fn bin() -> Command {
+    Command::cargo_bin("dotenv").unwrap()
+}
+
+fn env_path() -> String {
+    let here = Path::new(env!("CARGO_MANIFEST_DIR"));
+    here.join("tests/.env.test").to_string_lossy().to_string()
+}
+
+#[test]
+fn debug_reports_keys_and_file() {
+    bin()
+        .arg("NAME")
+        .arg("--debug")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .stdout("dotenv-cli\n")
+        .stderr(
+            predicate::str::contains("Keys: [\"NAME\"]")
+                .and(predicate::str::contains(".env.test"))
+                .and(predicate::str::contains("Options assembled")),
+        );
+}
+
+#[test]
+fn debug_reports_json_defaulting_and_wildcards() {
+    bin()
+        .arg("NESTED_*")
+        .arg("--debug")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .stderr(predicate::str::contains("Wildcard found"));
+}
+
+#[test]
+fn debug_reports_json_defaulting_for_multiple_keys() {
+    bin()
+        .arg("NAME")
+        .arg("EMPTY")
+        .arg("--debug")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .stderr(predicate::str::contains(
+            "Key count (0 or >1) defaulting to JSON",
+        ));
+}
+
+#[test]
+fn debug_reports_file_during_validate() {
+    bin()
+        .arg("--validate")
+        .arg("--debug")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .stderr(predicate::str::contains("File: "));
+}
+
+#[test]
+fn debug_reports_command_before_running_it() {
+    bin()
+        .arg("--debug")
+        .arg("--file")
+        .arg(env_path())
+        .arg("--")
+        .arg("true")
+        .assert()
+        .success()
+        .stderr(
+            predicate::str::contains("Command: [\"true\"]")
+                .and(predicate::str::contains("Running: true")),
+        );
+}
+
+#[test]
+fn debug_reports_variables_skipped_because_already_set() {
+    bin()
+        .arg("--debug")
+        .arg("--file")
+        .arg(env_path())
+        .env("NAME", "from-the-shell")
+        .arg("--")
+        .arg("true")
+        .assert()
+        .success()
+        .stderr(predicate::str::contains(
+            "Skipping NAME (already set in the environment)",
+        ));
+}
diff --git a/tests/wildcard.rs b/tests/wildcard.rs
new file mode 100644
index 0000000..b7847c5
--- /dev/null
+++ b/tests/wildcard.rs
@@ -0,0 +1,89 @@
+use assert_cmd::Command;
+use std::path::Path;
+
+fn bin() -> Command {
+    Command::cargo_bin("dotenv").unwrap()
+}
+
+fn env_path() -> String {
+    let here = Path::new(env!("CARGO_MANIFEST_DIR"));
+    here.join("tests/.env.test").to_string_lossy().to_string()
+}
+
+fn keys_for(pattern: &str) -> Vec<String> {
+    let output = bin()
+        .arg(pattern)
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .get_output()
+        .stdout
+        .clone();
+    let value: serde_json::Value = serde_json::from_slice(&output).unwrap();
+    value.as_object().unwrap().keys().cloned().collect()
+}
+
+#[test]
+fn trailing_wildcard_matches_by_prefix() {
+    assert_eq!(keys_for("NESTED_*"), vec!["NESTED_VAR1", "NESTED_VAR2"]);
+}
+
+#[test]
+fn leading_wildcard_matches_by_suffix() {
+    assert_eq!(
+        keys_for("*_MULTI"),
+        vec!["DOUBLE_MULTI", "SINGLE_MULTI", "CORRECT_MULTI"]
+    );
+}
+
+#[test]
+fn wildcard_on_both_sides_matches_the_middle() {
+    assert_eq!(keys_for("*_MULTI_*"), vec!["LIST_MULTI_LINE"]);
+}
+
+#[test]
+fn wildcard_output_resolves_nested_variables() {
+    bin()
+        .arg("NESTED_VAR2*")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .stdout("{\"NESTED_VAR2\":\"Hello World\"}\n");
+}
+
+#[test]
+fn wildcard_forces_json_even_for_a_single_match() {
+    bin()
+        .arg("NAM*")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .stdout("{\"NAME\":\"dotenv-cli\"}\n");
+}
+
+#[test]
+fn wildcard_matching_nothing_returns_an_empty_object_not_the_whole_file() {
+    bin()
+        .arg("ZZZ_*")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .success()
+        .stdout("{}\n");
+}
+
+#[test]
+fn no_json_disables_wildcard_expansion() {
+    // With --no-json the pattern is treated as a literal key name, which does
+    // not exist, so the lookup fails.
+    bin()
+        .arg("NESTED_*")
+        .arg("--no-json")
+        .arg("--file")
+        .arg(env_path())
+        .assert()
+        .failure();
+}